feat: implement receipt alias functionality with CRUD operations and integrate with receipt import

backend/prisma/schema.prisma

@@ -21,6 +21,7 @@ model Product {
   inventoryItems    InventoryItem[]
   recipeIngredients RecipeIngredient[]
   pantryItems       PantryItem[]
+  receiptAliases    ReceiptAlias[]
 }
 
 model InventoryItem {
@@ -95,6 +96,14 @@ model PantryItem {
   updatedAt DateTime @updatedAt
 }
 
+model ReceiptAlias {
+  id           Int      @id @default(autoincrement())
+  receiptName  String   @unique  // normaliserat kvittonamn (lowercase, trim)
+  productId    Int
+  product      Product  @relation(fields: [productId], references: [id], onDelete: Cascade)
+  createdAt    DateTime @default(now())
+}
+
 model MealPlanEntry {
   id        Int      @id @default(autoincrement())
   date      DateTime @db.Date