feat(server): blob reconciliation (#15165)

#### PR Dependency Tree


* **PR #15165** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added automated backend maintenance for missing blob metadata
backfill, document-to-blob reference rebuilding, and unreferenced blob
cleanup planning/execution.
* Introduced scheduled batch processing (workspace-paged) and paginated
object-storage listing.
* **Bug Fixes**
* Improved reliability of object-storage reads by treating expected “not
found” results as non-errors.
* Strengthened blob/expired cleanup flows with runtime-driven batching
and reduced coupling to metadata synchronization.
* **Tests**
* Expanded unit and e2e coverage for partial blob metadata and updated
runtime/job cleanup test assertions.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/base/job/queue/config.ts

@@ -94,4 +94,12 @@ defineModuleConfig('job', {
     },
     schema,
   },
+
+  'queues.backendRuntime': {
+    desc: 'The config for backend runtime job queue',
+    default: {
+      concurrency: 1,
+    },
+    schema,
+  },
 });

packages/backend/server/src/base/job/queue/def.ts

@@ -29,6 +29,7 @@ export enum Queue {
   COPILOT = 'copilot',
   INDEXER = 'indexer',
   CALENDAR = 'calendar',
+  BACKENDRUNTIME = 'backendRuntime',
 }
 
 export const QUEUES = Object.values(Queue);