feat: multipart blob sync support (#14138)

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

* **New Features**
* Flexible blob uploads: GRAPHQL, presigned, and multipart flows with
per‑part URLs, abort/complete operations, presigned proxy endpoints, and
nightly cleanup of expired pending uploads.

* **API / Schema**
* GraphQL additions: new types, mutations, enum and error to manage
upload lifecycle (create, complete, abort, get part URL).

* **Database**
* New blob status enum and columns (status, upload_id); listing now
defaults to completed blobs.

* **Localization**
  * Added user-facing message: "Blob is invalid."

* **Tests**
* Expanded unit and end‑to‑end coverage for upload flows, proxy
behavior, multipart and provider integrations.

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settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/models/blob.ts

@@ -21,12 +21,16 @@ export class BlobModel extends BaseModel {
       update: {
         mime: blob.mime,
         size: blob.size,
+        status: blob.status,
+        uploadId: blob.uploadId,
       },
       create: {
         workspaceId: blob.workspaceId,
         key: blob.key,
         mime: blob.mime,
         size: blob.size,
+        status: blob.status,
+        uploadId: blob.uploadId,
       },
     });
   }
@@ -76,11 +80,39 @@ export class BlobModel extends BaseModel {
         ...options?.where,
         workspaceId,
         deletedAt: null,
+        status: 'completed',
       },
       select: options?.select,
     });
   }
 
+  async hasAny(workspaceId: string) {
+    const count = await this.db.blob.count({
+      where: {
+        workspaceId,
+        deletedAt: null,
+      },
+    });
+    return count > 0;
+  }
+
+  async listPendingExpired(before: Date) {
+    return await this.db.blob.findMany({
+      where: {
+        status: 'pending',
+        deletedAt: null,
+        createdAt: {
+          lt: before,
+        },
+      },
+      select: {
+        workspaceId: true,
+        key: true,
+        uploadId: true,
+      },
+    });
+  }
+
   async listDeleted(workspaceId: string) {
     return await this.db.blob.findMany({
       where: {