feat(local_backend): reservations, print analytics, workday summary, zone-PIN management

- New reservations module: model, schema, router (CRUD + status updates + upcoming alerts)
  and background task for auto-expiring stale reservations
- Reports: print_products, print_categories, print_tables analytics endpoints
  plus meta_products and business_day_summary for workday close/view flow
- printer_service: configurable font sizes/weights, donut/bar chart print layout helpers,
  analytics print blocks per printer
- tables/schemas: surfaced color, zone, and other new fields on Table, Product, User, Printer
- demo_seed.py for quick dev DB population; wipe_database.py utility

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

local_backend/models/reservation.py

@@ -0,0 +1,42 @@
+from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Text
+from sqlalchemy.orm import relationship
+from datetime import datetime, timezone
+from database import Base
+
+
+class Reservation(Base):
+    __tablename__ = "reservations"
+
+    id = Column(Integer, primary_key=True, index=True)
+
+    # Guest info
+    guest_name = Column(String, nullable=False)
+    party_size = Column(Integer, nullable=False)
+    phone = Column(String, nullable=True)
+    email = Column(String, nullable=True)
+    note = Column(Text, nullable=True)
+
+    # When the customer wants the table
+    reserved_for = Column(DateTime, nullable=False)
+
+    # Optional table assignment (assignable/editable later)
+    table_id = Column(Integer, ForeignKey("tables.id"), nullable=True)
+
+    # Lifecycle: pending | arrived | cancelled | no_show
+    status = Column(String, nullable=False, default="pending")
+
+    # Source: manager_app | waiter_app | online
+    source = Column(String, nullable=False, default="manager_app")
+
+    # Who entered this reservation (staff user)
+    created_by_user_id = Column(Integer, ForeignKey("users.id"), nullable=True)
+
+    # For future online reservations: cloud-side customer identifier
+    online_customer_id = Column(String, nullable=True)
+
+    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc))
+    updated_at = Column(DateTime, default=lambda: datetime.now(timezone.utc),
+                        onupdate=lambda: datetime.now(timezone.utc))
+
+    table = relationship("Table", foreign_keys=[table_id])
+    created_by = relationship("User", foreign_keys=[created_by_user_id])