feat(products): include ownerId in product creation and enforce its requirement

backend/src/products/products.controller.ts

@@ -128,8 +128,8 @@ export class ProductsController {
 
   @Roles('admin')
   @Post()
-  create(@Body() body: CreateProductDto) {
-    return this.productsService.create(body);
+  create(@Body() body: CreateProductDto, @Request() req: { user: { id: number } }) {
+    return this.productsService.create(body, req.user.id);
   }
 
   // Tillgänglig för alla inloggade användare — req.user.id injiceras av JWT-guard

backend/src/products/products.service.ts

@@ -116,7 +116,7 @@ export class ProductsService {
     return product;
   }
 
-  async create(data: CreateProductDto) {
+  async create(data: CreateProductDto, ownerId?: number) {
     const name = data.name.trim();
     const normalizedName = normalizeName(name);
 
@@ -140,8 +140,13 @@ export class ProductsService {
       return existing;
     }
 
+    if (!ownerId) {
+      throw new Error('ownerId är obligatorisk för att skapa en produkt');
+    }
+
     return this.prisma.product.create({
       data: {
+        ownerId,
         name,
         normalizedName,
         canonicalName: name,