feat(inventory): add multi-country origin tracking

- Added `originCountries` field to `InventoryItem` model for multi-country origin support
- Updated `CreateInventoryDto` and `UpdateInventoryDto` with `originCountries` array field
- Modified `InventoryService` to handle `originCountries` in create and update operations
- Added `origin` field to `FlyerImportItem` response type for consistency
- Added `categoryId` field to `ParsedReceiptItem` DTO for improved receipt parsing
- Created database migration `20260524_add_origin_countries` for schema changes

backend/prisma/schema.prisma

@@ -104,6 +104,7 @@ model InventoryItem {
   unit           String
   brand		 String?
   origin         String?
+  originCountries Json?
   receiptName    String?
   location       String?
   purchaseDate   DateTime?