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/migrations/20260524_add_origin_countries/migration.sql

@@ -0,0 +1,9 @@
+-- Add originCountries field to InventoryItem table
+-- This migration adds support for multiple origin countries as a JSON array
+
+ALTER TABLE `InventoryItem` 
+ADD COLUMN `originCountries` JSON NULL 
+AFTER `origin`;
+
+-- Create an index for the originCountries field for better query performance
+CREATE INDEX `IDX_InventoryItem_originCountries` ON `InventoryItem` ((CAST(`originCountries` AS CHAR(255))));