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>

docs/implementation/order-item-exceptions.md

@@ -254,6 +254,30 @@ Response:
 }
 ```
 
+## Admin UI
+
+The exceptions tab is available in the Letzshop management page:
+
+**Location:** `/admin/marketplace/letzshop` → Exceptions tab
+
+### Features
+
+- **Stats Cards**: Shows pending, resolved, ignored, and affected orders counts
+- **Filters**: Search by GTIN/product name/order number, filter by status
+- **Exception Table**: Paginated list with product info, GTIN, order link, status
+- **Actions**:
+    - **Resolve**: Opens modal with product search (autocomplete)
+    - **Ignore**: Marks exception as ignored (still blocks confirmation)
+    - **Bulk Resolve**: Checkbox to apply resolution to all exceptions with same GTIN
+
+### Files
+
+| File | Description |
+|------|-------------|
+| `app/templates/admin/partials/letzshop-exceptions-tab.html` | Tab HTML template |
+| `app/templates/admin/marketplace-letzshop.html` | Main page (includes tab) |
+| `static/admin/js/marketplace-letzshop.js` | JavaScript handlers |
+
 ## Error Handling
 
 | Exception | HTTP Status | When |