feat(sync): add parallel sync, fix default branch and protected branch issues, add group avatars option

- Set sync concurrency to 10 for faster parallel repo syncing
- Three-phase push: push refs, sync default_branch via API, then push with --prune
- Unprotect stale protected branches on target before pruning
- Handle group visibility 400 errors gracefully (skip visibility, sync description only)
- Add useGroupAvatarsForProjects option: projects without avatars inherit group avatar
- Upgrade @apiclient.xyz/gitlab to v2.3.0 (getProtectedBranches, unprotectBranch)

ts_interfaces/requests/sync.ts

@@ -29,6 +29,7 @@ export interface IReq_CreateSyncConfig extends plugins.typedrequestInterfaces.im
     enforceDelete?: boolean;
     enforceGroupDelete?: boolean;
     addMirrorHint?: boolean;
+    useGroupAvatarsForProjects?: boolean;
   };
   response: {
     config: data.ISyncConfig;
@@ -49,6 +50,7 @@ export interface IReq_UpdateSyncConfig extends plugins.typedrequestInterfaces.im
     enforceDelete?: boolean;
     enforceGroupDelete?: boolean;
     addMirrorHint?: boolean;
+    useGroupAvatarsForProjects?: boolean;
   };
   response: {
     config: data.ISyncConfig;