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>

tests/unit/utils/test_csv_processor.py

@@ -148,17 +148,17 @@ TEST001,Product 1,Description 1,19.99 EUR,Brand1,Category1"""
         assert product_data["price"] == "19.99"
         assert product_data["brand"] == "TestBrand"
 
-    def test_parse_price_to_numeric(self):
-        """Test price string to numeric conversion"""
-        assert self.processor._parse_price_to_numeric("19.99 EUR") == 19.99
-        assert self.processor._parse_price_to_numeric("19,99 EUR") == 19.99
-        assert self.processor._parse_price_to_numeric("$29.99") == 29.99
-        assert self.processor._parse_price_to_numeric("100") == 100.0
-        assert self.processor._parse_price_to_numeric(None) is None
-        assert self.processor._parse_price_to_numeric("") is None
+    def test_parse_price_to_cents(self):
+        """Test price string to cents conversion"""
+        assert self.processor._parse_price_to_cents("19.99 EUR") == 1999
+        assert self.processor._parse_price_to_cents("19,99 EUR") == 1999
+        assert self.processor._parse_price_to_cents("$29.99") == 2999
+        assert self.processor._parse_price_to_cents("100") == 10000
+        assert self.processor._parse_price_to_cents(None) is None
+        assert self.processor._parse_price_to_cents("") is None
 
     def test_clean_row_data_with_prices(self):
-        """Test row data cleaning with price parsing"""
+        """Test row data cleaning with price parsing to cents"""
         row_data = {
             "marketplace_product_id": "TEST001",
             "title": "Test Product",
@@ -169,8 +169,8 @@ TEST001,Product 1,Description 1,19.99 EUR,Brand1,Category1"""
 
         cleaned = self.processor._clean_row_data(row_data)
 
-        assert cleaned["price_numeric"] == 19.99
-        assert cleaned["sale_price_numeric"] == 14.99
+        assert cleaned["price_cents"] == 1999  # Integer cents
+        assert cleaned["sale_price_cents"] == 1499  # Integer cents
         assert cleaned["currency"] == "EUR"
 
     @pytest.mark.asyncio