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/utils/csv_processor.py

@@ -18,6 +18,7 @@ import requests
 from sqlalchemy import literal
 from sqlalchemy.orm import Session
 
+from app.utils.money import euros_to_cents
 from models.database.marketplace_import_job import MarketplaceImportError
 from models.database.marketplace_product import MarketplaceProduct
 from models.database.marketplace_product_translation import (
@@ -154,8 +155,18 @@ class CSVProcessor:
         logger.info(f"Normalized columns: {list(df.columns)}")
         return df
 
-    def _parse_price_to_numeric(self, price_str: str | None) -> float | None:
-        """Parse price string like '19.99 EUR' to float."""
+    def _parse_price_to_cents(self, price_str: str | None) -> int | None:
+        """Parse price string like '19.99 EUR' to integer cents.
+
+        Uses the money utility for precise conversion.
+        Example: '19.99 EUR' -> 1999
+
+        Args:
+            price_str: Price string with optional currency
+
+        Returns:
+            Price in integer cents, or None if parsing fails
+        """
         if not price_str:
             return None
 
@@ -164,8 +175,9 @@ class CSVProcessor:
         if numbers:
             num_str = numbers[0].replace(",", ".")
             try:
-                return float(num_str)
-            except ValueError:
+                # Convert euros to cents using money utility
+                return euros_to_cents(num_str)
+            except (ValueError, TypeError):
                 pass
         return None
 
@@ -185,10 +197,10 @@ class CSVProcessor:
             parsed_price, currency = self.price_processor.parse_price_currency(
                 processed_data["price"]
             )
-            # Store both raw price string and numeric value
+            # Store both raw price string and numeric value in cents
             raw_price = processed_data["price"]
             processed_data["price"] = parsed_price
-            processed_data["price_numeric"] = self._parse_price_to_numeric(raw_price)
+            processed_data["price_cents"] = self._parse_price_to_cents(raw_price)
             processed_data["currency"] = currency
 
         # Process sale_price
@@ -198,7 +210,7 @@ class CSVProcessor:
                 processed_data["sale_price"]
             )
             processed_data["sale_price"] = parsed_sale_price
-            processed_data["sale_price_numeric"] = self._parse_price_to_numeric(
+            processed_data["sale_price_cents"] = self._parse_price_to_cents(
                 raw_sale_price
             )