feat(connect): Phase 2 — cloud DB models for Xenia Connect

Adds three new tables created automatically by create_all on next
startup, plus an additive migration for an existing table:

models/menu_snapshot.py (NEW)
  - menu_snapshots: one row per site, holds the full serialized
    category+product JSON; upserted on each sync from local_backend

models/online_order.py (NEW)
  - online_orders: full order lifecycle from customer submission
    through delivery; tracks sync state so local_backend can poll
    for unprocessed orders (synced_to_local=0)

models/manager_account.py (NEW)
  - manager_accounts + manager_site_access (M2M join table): remote
    manager login accounts with per-site access control

models/site.py (MODIFIED)
  - order_counter column added; incremented atomically when each
    online order is created to generate "ORD-XXXX" public_ref values

main.py (MODIFIED)
  - imports all three new models so create_all registers their tables
  - _run_migrations() added (same pattern as local_backend) for the
    additive order_counter column on the existing sites table

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

cloud_backend/models/online_order.py

@@ -0,0 +1,41 @@
+from sqlalchemy import Column, Integer, String, Text, Float, DateTime, ForeignKey
+from sqlalchemy.sql import func
+from database import Base
+
+
+class OnlineOrder(Base):
+    __tablename__ = "online_orders"
+
+    id = Column(Integer, primary_key=True, index=True)
+    site_id = Column(Integer, ForeignKey("sites.id"), nullable=False, index=True)
+
+    # Human-readable reference, unique per site (e.g. "ORD-0042")
+    public_ref = Column(String, unique=True, nullable=False)
+    order_type = Column(String, nullable=False)  # "delivery" | "dine_in"
+
+    # Customer info
+    customer_name = Column(String, nullable=False)
+    customer_phone = Column(String, nullable=True)
+    customer_address = Column(Text, nullable=True)   # required for delivery
+    customer_notes = Column(Text, nullable=True)
+
+    # Order content — JSON array of ordered items
+    items_json = Column(Text, nullable=False)
+
+    # Financials
+    subtotal = Column(Float, nullable=False)
+    delivery_fee = Column(Float, default=0.0, nullable=False)
+    total = Column(Float, nullable=False)
+
+    # Status lifecycle:
+    # pending_acceptance → accepted | rejected
+    # accepted → preparing → ready | out_for_delivery → delivered
+    status = Column(String, default="pending_acceptance", nullable=False, index=True)
+    rejection_reason = Column(String, nullable=True)
+
+    # Sync state — local backend polls for these
+    synced_to_local = Column(Integer, default=0, nullable=False)  # 0=no, 1=yes
+    local_order_id = Column(Integer, nullable=True)               # set after local creates it
+
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())