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)

package.json

@@ -17,7 +17,7 @@
     "@api.global/typedserver": "8.4.0",
     "@api.global/typedsocket": "^4.1.0",
     "@apiclient.xyz/gitea": "1.2.0",
-    "@apiclient.xyz/gitlab": "2.2.0",
+    "@apiclient.xyz/gitlab": "2.3.0",
     "@design.estate/dees-catalog": "^3.43.3",
     "@design.estate/dees-element": "^2.1.6"
   },