feat(migration): enforce ownerId requirement in Product table

- Removed all products without an owner to maintain data integrity.
- Updated ownerId column to be non-nullable.
- Modified foreign key constraint for ownerId to use ON DELETE CASCADE.

backend/prisma/migrations/20260502160000_product_owner_required/migration.sql

@@ -0,0 +1,17 @@
+-- Steg 1: Ta bort alla produkter utan ägare (globala seed-produkter)
+-- Detta tar automatiskt bort relaterade rader via ON DELETE CASCADE
+-- för: InventoryItem, PantryItem, ReceiptAlias, ProductTag, Nutrition, UserProduct
+DELETE FROM `Product` WHERE `ownerId` IS NULL;
+
+-- Steg 2: Gör ownerId obligatoriskt
+ALTER TABLE `Product`
+  MODIFY COLUMN `ownerId` INT NOT NULL;
+
+-- Steg 3: Uppdatera foreign key constraint till CASCADE (ta bort gammal, lägg till ny)
+ALTER TABLE `Product`
+  DROP FOREIGN KEY IF EXISTS `Product_ownerId_fkey`;
+
+ALTER TABLE `Product`
+  ADD CONSTRAINT `Product_ownerId_fkey`
+  FOREIGN KEY (`ownerId`) REFERENCES `User`(`id`)
+  ON DELETE CASCADE ON UPDATE CASCADE;

backend/prisma/schema.prisma

@@ -48,8 +48,8 @@ model Product {
   receiptAliases    ReceiptAlias[]
   tags              ProductTag[]
   nutrition         Nutrition?
-  ownerId           Int?
-  owner             User?           @relation(fields: [ownerId], references: [id], onDelete: SetNull)
+  ownerId           Int
+  owner             User            @relation(fields: [ownerId], references: [id], onDelete: Cascade)
   userProducts      UserProduct[]
   categoryId        Int?
   categoryRef       Category?       @relation(fields: [categoryId], references: [id], onDelete: SetNull)