fix(audit): sort milestones, sort JSON export, extract test helper

- Fix milestone section using unsorted repos list
- Apply --sort to --format json output
- Rename _sort_repos to sort_repos (now used by cli.py)
- Extract shared make_repo helper to tests/helpers.py
- Move exporter import to module level in cli.py

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/gitea_dashboard/cli.py

@@ -11,7 +11,8 @@ from rich.console import Console
 
 from gitea_dashboard.client import GiteaClient
 from gitea_dashboard.collector import collect_all
-from gitea_dashboard.display import render_dashboard
+from gitea_dashboard.display import render_dashboard, sort_repos
+from gitea_dashboard.exporter import export_json
 
 _DEFAULT_URL = "http://192.168.0.106:3000"
 
@@ -107,8 +108,7 @@ def main(argv: list[str] | None = None) -> None:
         sys.exit(1)
 
     if args.format == "json":
-        from gitea_dashboard.exporter import export_json
-
-        print(export_json(repos))  # noqa: T201
+        sorted_repos = sort_repos(repos, args.sort)
+        print(export_json(sorted_repos))  # noqa: T201
     else:
         render_dashboard(repos, sort_key=args.sort)