feat: add product review and rating system with schema update

apps/backend/prisma/schema.prisma

@@ -38,6 +38,7 @@ model Product {
   scent       Scent            @relation(fields: [scentId], references: [id])
   variants    ProductVariant[]
   images      ProductImage[]
+  reviews     Review[]
   createdAt   DateTime         @default(now())
   updatedAt   DateTime         @updatedAt
 
@@ -82,6 +83,7 @@ model Customer {
   email       String?
   phone       String?
   orders      Order[]
+  reviews     Review[]
   createdAt   DateTime @default(now())
   updatedAt   DateTime @updatedAt
 }
@@ -372,3 +374,21 @@ model LazadaOrderItem {
   shippingFee           Float        @default(0)
   status                String?
 }
+
+// ── Reviews ────────────────────────────────────────────────────────────────
+model Review {
+  id           Int      @id @default(autoincrement())
+  rating       Int      @default(5)
+  comment      String?
+  productId    Int
+  product      Product  @relation(fields: [productId], references: [id], onDelete: Cascade)
+  customerId   Int?
+  customer     Customer? @relation(fields: [customerId], references: [id], onDelete: SetNull)
+  customerName String?
+  isPublished  Boolean  @default(true)
+  createdAt    DateTime @default(now())
+  updatedAt    DateTime @updatedAt
+
+  @@index([productId])
+  @@index([customerId])
+}