refactor: full DDD + Clean Architecture refactor

- Hapus src/utils/ (17 files) + src/db/ (8 files) dead code
- Absorb 7 re-export stubs → real impl di lokasi DDD
- Buat src/infrastructure/di.ts (DI container)
- Rewrite 5 controllers pakai repository/DI
- Fix shared/utils imports, env.ts, routes, index.ts
- Update package.json build path migrate
- Lint clean, build clean

src/infrastructure/di.ts

@@ -0,0 +1,51 @@
+/**
+ * Dependency Injection container.
+ *
+ * Wires up singleton instances of all repositories and application services,
+ * making them available to controllers and other adapters without requiring
+ * a full DI framework.
+ *
+ * @module infrastructure/di
+ */
+
+import type { IBucketRepository } from '../domain/ports/bucket-repository';
+import type { IFilePartRepository } from '../domain/ports/file-part-repository';
+import type { IFileRepository } from '../domain/ports/file-repository';
+import type { IMultipartRepository } from '../domain/ports/multipart-repository';
+import type { ITelegramService } from '../domain/ports/telegram-service';
+import { DrizzleBucketRepository } from './persistence/repositories/bucket-repository';
+import { DrizzleFilePartRepository } from './persistence/repositories/file-part-repository';
+import { DrizzleFileRepository } from './persistence/repositories/file-repository';
+import { DrizzleMultipartRepository } from './persistence/repositories/multipart-repository';
+import { botPool } from './telegram/bot-pool';
+import { ChunkedStorage } from './telegram/chunked-storage';
+import { UploadBatcher } from './telegram/upload-batcher';
+
+// ─── Repository Singletons ──────────────────────────────────────────
+
+/** Singleton IFileRepository instance backed by Drizzle ORM. */
+export const fileRepository: IFileRepository = new DrizzleFileRepository();
+
+/** Singleton IBucketRepository instance backed by Drizzle ORM. */
+export const bucketRepository: IBucketRepository = new DrizzleBucketRepository();
+
+/** Singleton IFilePartRepository instance backed by Drizzle ORM. */
+export const filePartRepository: IFilePartRepository = new DrizzleFilePartRepository();
+
+/** Singleton IMultipartRepository instance backed by Drizzle ORM. */
+export const multipartRepository: IMultipartRepository = new DrizzleMultipartRepository();
+
+/** Singleton ITelegramService instance backed by the bot pool. */
+export const telegramService: ITelegramService = botPool;
+
+// ─── Service Singletons ─────────────────────────────────────────────
+
+/** Singleton ChunkedStorage for large file chunked uploads. */
+export const chunkedStorage = new ChunkedStorage(
+  fileRepository,
+  filePartRepository,
+  telegramService,
+);
+
+/** Singleton UploadBatcher for batched small-file uploads. */
+export const uploadBatcher = new UploadBatcher(fileRepository, telegramService);