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/printer.py

@@ -12,6 +12,7 @@ class Printer(Base):
     port = Column(Integer, default=9100, nullable=False)
     is_active = Column(Boolean, default=True, nullable=False)
     protocol = Column(String, default="escpos_tcp", nullable=False)
+    line_width = Column(Integer, default=48, nullable=False)
 
     products = relationship("Product", back_populates="printer_zone")
     print_logs = relationship("PrintLog", back_populates="printer")