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>

app/services/order_item_exception_service.py

@@ -329,8 +329,9 @@ class OrderItemExceptionService:
         order_item.needs_product_match = False
 
         # Update product snapshot on order item
-        order_item.product_name = product.get_title("en")  # Default to English
-        order_item.product_sku = product.sku or order_item.product_sku
+        if product.marketplace_product:
+            order_item.product_name = product.marketplace_product.get_title("en")
+        order_item.product_sku = product.vendor_sku or order_item.product_sku
 
         db.flush()
 
@@ -446,7 +447,8 @@ class OrderItemExceptionService:
             order_item = exception.order_item
             order_item.product_id = product_id
             order_item.needs_product_match = False
-            order_item.product_name = product.get_title("en")
+            if product.marketplace_product:
+                order_item.product_name = product.marketplace_product.get_title("en")
 
             resolved.append(exception)
 
@@ -613,7 +615,8 @@ class OrderItemExceptionService:
             order_item = exception.order_item
             order_item.product_id = product_id
             order_item.needs_product_match = False
-            order_item.product_name = product.get_title("en")
+            if product.marketplace_product:
+                order_item.product_name = product.marketplace_product.get_title("en")
 
         db.flush()