feat: Phase 2G — pay-later tab system

Backend:
- New models: Tab, TabEntry, TabPayment (3 new tables)
  - Tab: open|closed|forgiven, one open tab per customer enforced
  - TabEntry: what went ON the tab (per-item snapshot with description)
  - TabPayment: what came OFF the tab; balance = sum(entries) - sum(payments), never stored
- New router /api/tabs/:
  - GET / — list open tabs (sorted by balance desc); ?tab_status= override
  - GET /{id} — full tab detail with entries + payments
  - POST / — open new tab for a customer (400 if one already exists)
  - POST /{id}/entries — add entry directly (amount + description)
  - POST /{id}/pay — record payment; validates amount <= balance
  - POST /{id}/close — close tab (requires balance = 0)
  - POST /{id}/forgive — write off remaining balance
  - GET /customer/{customer_id} — all tabs for a customer (open first)
- POST /api/orders/{id}/items/{item_id}/tab:
  - Requires order has a customer assigned
  - Finds or auto-creates open tab for that customer
  - Sets order_item.status = "tabbed" (new valid status value)
  - Creates TabEntry with auto-generated description
  - Broadcasts order_updated SSE event
- Migrations: CREATE TABLE IF NOT EXISTS for tabs, tab_entries, tab_payments

Frontend:
- TabsPage (/tabs): open tabs list sorted by balance; each card shows charges/payments
  history, live balance, Πληρωμή modal (defaults to full balance), Κλείσιμο button
  (only shown when balance=0), Χάρισμα Υπολοίπου with confirm modal + reason
- CustomersPage CustomerDetail: open tab banner showing balance + entry count
  (appears between stats and contact info when customer has an open tab)
- OrderDetailPage: 📋 Καρτέλα button appears on active items when order has a customer;
  tabbed items show a 📋 Καρτέλα badge; tabItem mutation calls /items/{id}/tab
- Sidebar: CreditCard icon for Καρτέλες (after Πελάτες)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

local_backend/main.py

@@ -23,6 +23,7 @@ import models.reservation   # noqa: F401
 import models.notes          # noqa: F401 — registers SiteNote, SiteTodo
 import models.expenses       # noqa: F401 — registers Contact, Expense, ExpensePayment
 import models.customers      # noqa: F401 — registers Customer
+import models.tabs           # noqa: F401 — registers Tab, TabEntry, TabPayment
 
 from routers import auth, tables, products, orders, waiters, reports, system, setup as setup_router
 from routers import business_day as business_day_router
@@ -37,6 +38,7 @@ from routers import reservations as reservations_router
 from routers import notes as notes_router
 from routers.expenses import contacts_router, expenses_router
 from routers import customers as customers_router
+from routers import tabs as tabs_router
 
 
 def _run_migrations():
@@ -275,6 +277,35 @@ def _run_migrations():
         # Phase 2B — staff payroll
         "ALTER TABLE users ADD COLUMN hourly_rate REAL",
         "ALTER TABLE waiter_shifts ADD COLUMN hourly_rate_snapshot REAL",
+        # Phase 2G — pay-later tab system
+        """CREATE TABLE IF NOT EXISTS tabs (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            customer_id INTEGER NOT NULL REFERENCES customers(id),
+            status VARCHAR NOT NULL DEFAULT 'open',
+            opened_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+            closed_at DATETIME,
+            closed_by_id INTEGER REFERENCES users(id),
+            notes TEXT
+        )""",
+        """CREATE TABLE IF NOT EXISTS tab_entries (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            tab_id INTEGER NOT NULL REFERENCES tabs(id),
+            order_id INTEGER REFERENCES orders(id),
+            order_item_id INTEGER REFERENCES order_items(id),
+            amount REAL NOT NULL,
+            description TEXT,
+            created_by_id INTEGER NOT NULL REFERENCES users(id),
+            created_at DATETIME DEFAULT CURRENT_TIMESTAMP
+        )""",
+        """CREATE TABLE IF NOT EXISTS tab_payments (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            tab_id INTEGER NOT NULL REFERENCES tabs(id),
+            amount REAL NOT NULL,
+            payment_method VARCHAR,
+            received_by_id INTEGER NOT NULL REFERENCES users(id),
+            notes TEXT,
+            created_at DATETIME DEFAULT CURRENT_TIMESTAMP
+        )""",
         # Phase 2F — customer CRM
         """CREATE TABLE IF NOT EXISTS customers (
             id INTEGER PRIMARY KEY AUTOINCREMENT,
@@ -412,3 +443,4 @@ app.include_router(notes_router.router,          prefix="/api/notes",        tag
 app.include_router(contacts_router,              prefix="/api/contacts",     tags=["contacts"])
 app.include_router(expenses_router,              prefix="/api/expenses",     tags=["expenses"])
 app.include_router(customers_router.router,      prefix="/api/customers",    tags=["customers"])
+app.include_router(tabs_router.router,           prefix="/api/tabs",         tags=["tabs"])

local_backend/models/tabs.py

@@ -0,0 +1,58 @@
+from sqlalchemy import Column, Integer, String, Boolean, DateTime, Float, ForeignKey, Text
+from sqlalchemy.orm import relationship
+from datetime import datetime, timezone
+from database import Base
+
+
+def _utcnow():
+    return datetime.now(timezone.utc)
+
+
+class Tab(Base):
+    __tablename__ = "tabs"
+
+    id = Column(Integer, primary_key=True, index=True)
+    customer_id = Column(Integer, ForeignKey("customers.id"), nullable=False)
+    status = Column(String, default="open", nullable=False)  # open | closed | forgiven
+    opened_at = Column(DateTime(timezone=True), default=_utcnow)
+    closed_at = Column(DateTime(timezone=True), nullable=True)
+    closed_by_id = Column(Integer, ForeignKey("users.id"), nullable=True)
+    notes = Column(Text, nullable=True)
+
+    customer = relationship("Customer", foreign_keys=[customer_id])
+    closed_by = relationship("User", foreign_keys=[closed_by_id])
+    entries = relationship("TabEntry", back_populates="tab", cascade="all, delete-orphan")
+    payments = relationship("TabPayment", back_populates="tab", cascade="all, delete-orphan")
+
+
+class TabEntry(Base):
+    """What went ON the tab — a deferred charge."""
+    __tablename__ = "tab_entries"
+
+    id = Column(Integer, primary_key=True, index=True)
+    tab_id = Column(Integer, ForeignKey("tabs.id"), nullable=False)
+    order_id = Column(Integer, ForeignKey("orders.id"), nullable=True)
+    order_item_id = Column(Integer, ForeignKey("order_items.id"), nullable=True)
+    amount = Column(Float, nullable=False)          # snapshot at time of tab entry
+    description = Column(Text, nullable=True)       # auto-generated summary
+    created_by_id = Column(Integer, ForeignKey("users.id"), nullable=False)
+    created_at = Column(DateTime(timezone=True), default=_utcnow)
+
+    tab = relationship("Tab", back_populates="entries")
+    created_by = relationship("User", foreign_keys=[created_by_id])
+
+
+class TabPayment(Base):
+    """What came OFF the tab — a payment reducing the balance."""
+    __tablename__ = "tab_payments"
+
+    id = Column(Integer, primary_key=True, index=True)
+    tab_id = Column(Integer, ForeignKey("tabs.id"), nullable=False)
+    amount = Column(Float, nullable=False)
+    payment_method = Column(String, nullable=True)  # cash | card | other
+    received_by_id = Column(Integer, ForeignKey("users.id"), nullable=False)
+    notes = Column(Text, nullable=True)
+    created_at = Column(DateTime(timezone=True), default=_utcnow)
+
+    tab = relationship("Tab", back_populates="payments")
+    received_by = relationship("User", foreign_keys=[received_by_id])

local_backend/routers/orders.py

@@ -583,6 +583,10 @@ class AssignCustomerBody(BaseModel):
     customer_id: Optional[int] = None  # null = unassign
 
 
+class TabItemBody(BaseModel):
+    pass  # no body needed — tab derived from order's customer
+
+
 @router.put("/{order_id}/customer")
 def assign_customer(order_id: int, body: AssignCustomerBody, db: Session = Depends(get_db), user: User = Depends(require_manager)):
     from models.customers import Customer
@@ -958,3 +962,55 @@ def print_synopsis(
 
     background_tasks.add_task(print_order_synopsis, printer.ip_address, printer.port, synopsis, printer.line_width)
     return {"status": "printing"}
+
+
+# ─── Phase 2G: Put item on customer tab ───────────────────────────────────────
+
+@router.post("/{order_id}/items/{item_id}/tab")
+def put_item_on_tab(
+    order_id: int,
+    item_id: int,
+    db: Session = Depends(get_db),
+    user: User = Depends(require_manager),
+):
+    from models.tabs import Tab, TabEntry
+
+    order = db.query(Order).filter(Order.id == order_id).first()
+    if not order:
+        raise HTTPException(status_code=404, detail="Order not found")
+    if not order.customer_id:
+        raise HTTPException(status_code=400, detail="Order has no customer assigned — assign a customer first")
+
+    item = db.query(OrderItem).filter(OrderItem.id == item_id, OrderItem.order_id == order_id).first()
+    if not item:
+        raise HTTPException(status_code=404, detail="Item not found")
+    if item.status != "active":
+        raise HTTPException(status_code=400, detail=f"Item is already {item.status} — cannot tab it")
+
+    # Find or auto-create the customer's open tab
+    tab = db.query(Tab).filter(Tab.customer_id == order.customer_id, Tab.status == "open").first()
+    if not tab:
+        tab = Tab(customer_id=order.customer_id)
+        db.add(tab)
+        db.flush()
+
+    # Build description
+    product_name = item.product.name if item.product else f"#{item.product_id}"
+    description = f"{product_name} ×{item.quantity} @ €{item.unit_price:.2f}"
+
+    entry = TabEntry(
+        tab_id=tab.id,
+        order_id=order_id,
+        order_item_id=item_id,
+        amount=round(item.unit_price * item.quantity, 2),
+        description=description,
+        created_by_id=user.id,
+    )
+    db.add(entry)
+
+    # Mark item as tabbed — distinct from active/paid/cancelled
+    item.status = "tabbed"
+
+    db.commit()
+    broadcast_sync("order_updated", {"order_id": order.id, "table_id": order.table_id, "status": order.status, "action": "item_tabbed"})
+    return {"status": "tabbed", "tab_id": tab.id, "entry_amount": entry.amount}

local_backend/routers/tabs.py

@@ -0,0 +1,223 @@
+from datetime import datetime, timezone
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+from typing import List, Optional
+
+from database import get_db
+from models.tabs import Tab, TabEntry, TabPayment
+from models.customers import Customer
+from models.order import Order, OrderItem
+from models.user import User
+from schemas.tabs import TabOut, TabEntryOut, TabPaymentOut, TabPayRequest, TabForgiveRequest, TabCloseRequest
+from routers.deps import require_manager
+
+router = APIRouter()
+
+
+def _utcnow():
+    return datetime.now(timezone.utc)
+
+
+def _tab_out(tab: Tab) -> dict:
+    c = tab.customer
+    customer_name = c.name if c else None
+    if c and c.nickname:
+        customer_name = f"{c.name} «{c.nickname}»"
+    customer_phone = c.phone if c else None
+
+    total_charged = round(sum(e.amount for e in tab.entries), 2)
+    total_paid = round(sum(p.amount for p in tab.payments), 2)
+    balance = round(total_charged - total_paid, 2)
+
+    closed_by_name = None
+    if tab.closed_by:
+        closed_by_name = tab.closed_by.full_name or tab.closed_by.username
+
+    entries_out = []
+    for e in sorted(tab.entries, key=lambda x: x.created_at):
+        creator = e.created_by.full_name or e.created_by.username if e.created_by else None
+        entries_out.append({
+            "id": e.id, "tab_id": e.tab_id, "order_id": e.order_id,
+            "order_item_id": e.order_item_id, "amount": e.amount,
+            "description": e.description, "created_by_id": e.created_by_id,
+            "created_by_name": creator, "created_at": e.created_at,
+        })
+
+    payments_out = []
+    for p in sorted(tab.payments, key=lambda x: x.created_at):
+        receiver = p.received_by.full_name or p.received_by.username if p.received_by else None
+        payments_out.append({
+            "id": p.id, "tab_id": p.tab_id, "amount": p.amount,
+            "payment_method": p.payment_method, "received_by_id": p.received_by_id,
+            "received_by_name": receiver, "notes": p.notes, "created_at": p.created_at,
+        })
+
+    return {
+        "id": tab.id,
+        "customer_id": tab.customer_id,
+        "customer_name": customer_name,
+        "customer_phone": customer_phone,
+        "status": tab.status,
+        "opened_at": tab.opened_at,
+        "closed_at": tab.closed_at,
+        "closed_by_id": tab.closed_by_id,
+        "notes": tab.notes,
+        "balance": balance,
+        "total_charged": total_charged,
+        "total_paid": total_paid,
+        "entries": entries_out,
+        "payments": payments_out,
+    }
+
+
+@router.get("/", response_model=List[TabOut])
+def list_tabs(
+    tab_status: Optional[str] = None,
+    customer_id: Optional[int] = None,
+    db: Session = Depends(get_db),
+    user: User = Depends(require_manager),
+):
+    q = db.query(Tab)
+    if tab_status:
+        q = q.filter(Tab.status == tab_status)
+    else:
+        q = q.filter(Tab.status == "open")  # default: only open tabs
+    if customer_id:
+        q = q.filter(Tab.customer_id == customer_id)
+    tabs = q.order_by(Tab.opened_at.desc()).all()
+    result = [_tab_out(t) for t in tabs]
+    # Sort open tabs by balance descending
+    result.sort(key=lambda x: x["balance"], reverse=True)
+    return result
+
+
+@router.get("/{tab_id}", response_model=TabOut)
+def get_tab(tab_id: int, db: Session = Depends(get_db), user: User = Depends(require_manager)):
+    tab = db.query(Tab).filter(Tab.id == tab_id).first()
+    if not tab:
+        raise HTTPException(status_code=404, detail="Tab not found")
+    return _tab_out(tab)
+
+
+@router.post("/", response_model=TabOut, status_code=status.HTTP_201_CREATED)
+def open_tab(customer_id: int, db: Session = Depends(get_db), user: User = Depends(require_manager)):
+    customer = db.query(Customer).filter(Customer.id == customer_id, Customer.is_active == True).first()
+    if not customer:
+        raise HTTPException(status_code=404, detail="Customer not found")
+    existing = db.query(Tab).filter(Tab.customer_id == customer_id, Tab.status == "open").first()
+    if existing:
+        raise HTTPException(status_code=400, detail="Customer already has an open tab")
+    tab = Tab(customer_id=customer_id)
+    db.add(tab)
+    db.commit()
+    db.refresh(tab)
+    return _tab_out(tab)
+
+
+@router.post("/{tab_id}/entries", response_model=TabOut)
+def add_tab_entry(
+    tab_id: int,
+    order_id: Optional[int] = None,
+    order_item_id: Optional[int] = None,
+    amount: float = 0.0,
+    description: Optional[str] = None,
+    db: Session = Depends(get_db),
+    user: User = Depends(require_manager),
+):
+    tab = db.query(Tab).filter(Tab.id == tab_id, Tab.status == "open").first()
+    if not tab:
+        raise HTTPException(status_code=404, detail="Open tab not found")
+    if amount <= 0:
+        raise HTTPException(status_code=400, detail="Amount must be positive")
+    entry = TabEntry(
+        tab_id=tab_id, order_id=order_id, order_item_id=order_item_id,
+        amount=amount, description=description, created_by_id=user.id,
+    )
+    db.add(entry)
+    db.commit()
+    db.refresh(tab)
+    return _tab_out(tab)
+
+
+@router.post("/{tab_id}/pay", response_model=TabOut)
+def pay_tab(
+    tab_id: int,
+    body: TabPayRequest,
+    db: Session = Depends(get_db),
+    user: User = Depends(require_manager),
+):
+    tab = db.query(Tab).filter(Tab.id == tab_id, Tab.status == "open").first()
+    if not tab:
+        raise HTTPException(status_code=404, detail="Open tab not found")
+    if body.amount <= 0:
+        raise HTTPException(status_code=400, detail="Amount must be positive")
+    total_charged = sum(e.amount for e in tab.entries)
+    total_paid = sum(p.amount for p in tab.payments)
+    balance = total_charged - total_paid
+    if body.amount > balance + 0.005:
+        raise HTTPException(status_code=400, detail=f"Payment exceeds balance ({balance:.2f})")
+    payment = TabPayment(
+        tab_id=tab_id, amount=body.amount,
+        payment_method=body.payment_method, notes=body.notes,
+        received_by_id=user.id,
+    )
+    db.add(payment)
+    db.commit()
+    db.refresh(tab)
+    return _tab_out(tab)
+
+
+@router.post("/{tab_id}/close", response_model=TabOut)
+def close_tab(
+    tab_id: int,
+    body: TabCloseRequest,
+    db: Session = Depends(get_db),
+    user: User = Depends(require_manager),
+):
+    tab = db.query(Tab).filter(Tab.id == tab_id, Tab.status == "open").first()
+    if not tab:
+        raise HTTPException(status_code=404, detail="Open tab not found")
+    total_charged = sum(e.amount for e in tab.entries)
+    total_paid = sum(p.amount for p in tab.payments)
+    balance = round(total_charged - total_paid, 2)
+    if balance > 0.005:
+        raise HTTPException(status_code=400, detail=f"Tab still has a balance of €{balance:.2f} — pay it off first or use /forgive")
+    tab.status = "closed"
+    tab.closed_at = _utcnow()
+    tab.closed_by_id = user.id
+    if body.notes:
+        tab.notes = body.notes
+    db.commit()
+    db.refresh(tab)
+    return _tab_out(tab)
+
+
+@router.post("/{tab_id}/forgive", response_model=TabOut)
+def forgive_tab(
+    tab_id: int,
+    body: TabForgiveRequest,
+    db: Session = Depends(get_db),
+    user: User = Depends(require_manager),
+):
+    tab = db.query(Tab).filter(Tab.id == tab_id, Tab.status == "open").first()
+    if not tab:
+        raise HTTPException(status_code=404, detail="Open tab not found")
+    tab.status = "forgiven"
+    tab.closed_at = _utcnow()
+    tab.closed_by_id = user.id
+    if body.reason:
+        tab.notes = body.reason
+    db.commit()
+    db.refresh(tab)
+    return _tab_out(tab)
+
+
+# ── Customer tabs ──────────────────────────────────────────────────────────────
+
+@router.get("/customer/{customer_id}", response_model=List[TabOut])
+def customer_tabs(customer_id: int, db: Session = Depends(get_db), user: User = Depends(require_manager)):
+    tabs = db.query(Tab).filter(Tab.customer_id == customer_id).order_by(
+        Tab.status.asc(),  # open first
+        Tab.opened_at.desc(),
+    ).all()
+    return [_tab_out(t) for t in tabs]

local_backend/schemas/tabs.py

@@ -0,0 +1,63 @@
+from pydantic import BaseModel
+from typing import Optional, List
+from datetime import datetime
+
+
+class TabEntryOut(BaseModel):
+    id: int
+    tab_id: int
+    order_id: Optional[int] = None
+    order_item_id: Optional[int] = None
+    amount: float
+    description: Optional[str] = None
+    created_by_id: int
+    created_by_name: Optional[str] = None
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class TabPaymentOut(BaseModel):
+    id: int
+    tab_id: int
+    amount: float
+    payment_method: Optional[str] = None
+    received_by_id: int
+    received_by_name: Optional[str] = None
+    notes: Optional[str] = None
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class TabOut(BaseModel):
+    id: int
+    customer_id: int
+    customer_name: Optional[str] = None
+    customer_phone: Optional[str] = None
+    status: str
+    opened_at: datetime
+    closed_at: Optional[datetime] = None
+    closed_by_id: Optional[int] = None
+    notes: Optional[str] = None
+    balance: float = 0.0          # computed: sum(entries) - sum(payments)
+    total_charged: float = 0.0
+    total_paid: float = 0.0
+    entries: List[TabEntryOut] = []
+    payments: List[TabPaymentOut] = []
+
+    model_config = {"from_attributes": True}
+
+
+class TabPayRequest(BaseModel):
+    amount: float
+    payment_method: Optional[str] = None
+    notes: Optional[str] = None
+
+
+class TabForgiveRequest(BaseModel):
+    reason: Optional[str] = None
+
+
+class TabCloseRequest(BaseModel):
+    notes: Optional[str] = None