feat: implement BackupTransferRunner for managing backup processes and enhance backup handling

src/types/index.ts

@@ -2,6 +2,7 @@
 export interface Env {
   DB: D1Database;
   NOTIFICATIONS_HUB: DurableObjectNamespace;
+  BACKUP_TRANSFER_RUNNER: DurableObjectNamespace;
   ASSETS?: {
     fetch(input: RequestInfo | URL, init?: RequestInit): Promise<Response>;
   };