feat: make pantry items and meal plan entries user-scoped; update related services and controllers

backend/prisma/schema.prisma

@@ -23,6 +23,8 @@ model User {
   ownedRecipes Recipe[]      @relation("RecipeOwner")
   sharedRecipes RecipeShare[]
   ownedProducts Product[]
+  pantryItems PantryItem[]
+  mealPlanEntries MealPlanEntry[]
 }
 
 model Product {
@@ -160,10 +162,15 @@ model RecipeIngredient {
 
 model PantryItem {
   id        Int      @id @default(autoincrement())
-  productId Int      @unique
+  userId    Int
+  productId Int
+  user      User     @relation(fields: [userId], references: [id], onDelete: Cascade)
   product   Product  @relation(fields: [productId], references: [id], onDelete: Cascade)
   createdAt DateTime @default(now())
   updatedAt DateTime @updatedAt
+
+  @@unique([userId, productId])
+  @@index([userId])
 }
 
 model ReceiptAlias {
@@ -176,14 +183,17 @@ model ReceiptAlias {
 
 model MealPlanEntry {
   id        Int      @id @default(autoincrement())
+  userId    Int
   date      DateTime @db.Date
   recipe    Recipe   @relation(fields: [recipeId], references: [id], onDelete: Cascade)
   recipeId  Int
+  user      User     @relation(fields: [userId], references: [id], onDelete: Cascade)
   servings  Int?
   createdAt DateTime @default(now())
   updatedAt DateTime @updatedAt
 
-  @@unique([date])
+  @@unique([userId, date])   # Bara ett recept per dag och användare
+  @@index([userId])
   @@index([date])
 }