fix: tags không có trong csdl gây nên lỗi crash backend

backend/prisma/migrations/20260616041407_sync_tags_column/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "Tour" ADD COLUMN     "tags" TEXT[];

backend/prisma/schema.prisma

@@ -90,6 +90,7 @@ model Tour {
   childCount    Int        @default(0)
   childDiscount Int        @default(30)
   
+  tags        String[]
   createdById String
   creator     User         @relation("TourCreator", fields: [createdById], references: [id])