feat: integer cents money handling, order page fixes, and vendor filter persistence

Money Handling Architecture:
- Store all monetary values as integer cents (€105.91 = 10591)
- Add app/utils/money.py with Money class and conversion helpers
- Add static/shared/js/money.js for frontend formatting
- Update all database models to use _cents columns (Product, Order, etc.)
- Update CSV processor to convert prices to cents on import
- Add Alembic migration for Float to Integer conversion
- Create .architecture-rules/money.yaml with 7 validation rules
- Add docs/architecture/money-handling.md documentation

Order Details Page Fixes:
- Fix customer name showing 'undefined undefined' - use flat field names
- Fix vendor info empty - add vendor_name/vendor_code to OrderDetailResponse
- Fix shipping address using wrong nested object structure
- Enrich order detail API response with vendor info

Vendor Filter Persistence Fixes:
- Fix orders.js: restoreSavedVendor now sets selectedVendor and filters
- Fix orders.js: init() only loads orders if no saved vendor to restore
- Fix marketplace-letzshop.js: restoreSavedVendor calls selectVendor()
- Fix marketplace-letzshop.js: clearVendorSelection clears TomSelect dropdown
- Align vendor selector placeholder text between pages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

models/database/letzshop.py

@@ -52,6 +52,19 @@ class VendorLetzshopCredentials(Base, TimestampMixin):
     auto_sync_enabled = Column(Boolean, default=False)
     sync_interval_minutes = Column(Integer, default=15)
 
+    # Test mode (disables API mutations when enabled)
+    test_mode_enabled = Column(Boolean, default=False)
+
+    # Default carrier settings
+    default_carrier = Column(String(50), nullable=True)  # greco, colissimo, xpresslogistics
+
+    # Carrier label URL prefixes
+    carrier_greco_label_url = Column(
+        String(500), default="https://dispatchweb.fr/Tracky/Home/"
+    )
+    carrier_colissimo_label_url = Column(String(500), nullable=True)
+    carrier_xpresslogistics_label_url = Column(String(500), nullable=True)
+
     # Last sync status
     last_sync_at = Column(DateTime(timezone=True), nullable=True)
     last_sync_status = Column(String(50), nullable=True)  # success, failed, partial