Add single-image zk and hotlink upload API with service tests.

Replace batch DTOs with per-mode endpoints, persist ciphertext with file-type
checks, and return a hashed delete token for future revocation.

backend/src/modules/upload/UploadModule.ts

@@ -1,10 +1,15 @@
 import { Module } from '@nestjs/common';
 import { TypeOrmModule } from '@nestjs/typeorm';
+import { StorageModule } from '../storage/StorageModule';
+import { UploadController } from './controllers/UploadController';
 import { Upload } from './entities/Upload';
 import { UploadHotlink } from './entities/UploadHotlink';
 import { UploadZk } from './entities/UploadZk';
+import { UploadService } from './services/UploadService';
 
 @Module({
-    imports: [TypeOrmModule.forFeature([Upload, UploadZk, UploadHotlink])]
+    imports: [TypeOrmModule.forFeature([Upload, UploadZk, UploadHotlink]), StorageModule],
+    controllers: [UploadController],
+    providers: [UploadService]
 })
 export class UploadModule {}