feat: chuẩn bị backend cho tính năng anonymous user upload ảnh không cần đăng nhập

backend/prisma/migrations/20260619014336_feat_anonymous_users/migration.sql

@@ -0,0 +1,15 @@
+-- DropForeignKey
+ALTER TABLE "Photo" DROP CONSTRAINT "Photo_tourId_fkey";
+
+-- AlterTable
+ALTER TABLE "Photo" ADD COLUMN     "originalUrl" TEXT,
+ALTER COLUMN "tourId" DROP NOT NULL,
+ALTER COLUMN "imageUrl" DROP NOT NULL;
+
+-- AlterTable
+ALTER TABLE "User" ADD COLUMN     "isAnonymous" BOOLEAN NOT NULL DEFAULT false,
+ALTER COLUMN "email" DROP NOT NULL,
+ALTER COLUMN "passwordHash" DROP NOT NULL;
+
+-- AddForeignKey
+ALTER TABLE "Photo" ADD CONSTRAINT "Photo_tourId_fkey" FOREIGN KEY ("tourId") REFERENCES "Tour"("id") ON DELETE SET NULL ON UPDATE CASCADE;

backend/prisma/schema.prisma

@@ -57,8 +57,8 @@ enum PrivacyLevel {
 
 model User {
   id            String        @id @default(uuid())
-  email         String        @unique
-  passwordHash  String
+  email         String?       @unique
+  passwordHash  String?
   name          String?
   phone         String?
   address       String?
@@ -66,6 +66,7 @@ model User {
   createdAt     DateTime      @default(now())
   isAdmin       Boolean       @default(false)
   isBlocked     Boolean       @default(false)
+  isAnonymous   Boolean       @default(false)
   
   createdTours            Tour[]              @relation("TourCreator")
   tourParticipations      TourParticipant[]