feat(store): add two-level store categories for admin and partner open-store

Admin CRUD under stores menu; partner picks leaf category on create.
Default sync only inserts missing rows and never updates existing ones.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/dukang-api/prisma/schema.v31.prisma

@@ -335,12 +335,18 @@ model CommonProductItem {
 }
 
 model CommonStoreCategory {
-  id    BigInt  @id @default(autoincrement()) @db.UnsignedBigInt
-  code  String  @unique @db.VarChar(32)
-  name  String  @db.VarChar(64)
-  sort  Int     @default(0)
-  stores Store[]
+  id       BigInt  @id @default(autoincrement()) @db.UnsignedBigInt
+  code     String  @unique @db.VarChar(32)
+  name     String  @db.VarChar(64)
+  sort     Int     @default(0)
+  parentId BigInt? @map("parent_id") @db.UnsignedBigInt
+  status   String  @default("ACTIVE") @db.VarChar(16)
+  parent   CommonStoreCategory?  @relation("StoreCategoryTree", fields: [parentId], references: [id], onDelete: Restrict)
+  children CommonStoreCategory[] @relation("StoreCategoryTree")
+  stores   Store[]
 
+  @@index([parentId, sort])
+  @@index([status])
   @@map("common_store_category")
 }