fix: missing team report system

[hadiafifah]

Summary

This PR adds an admin recovery flow for missing teams: admins can now mark a team as present and restore it back to relevant judges’ queues.

What Changed

Backend

• Added restoreMissingTeam(team_id) in the teams missing-report action module.
• Enforced admin-only access inside the action (auth() + role check).
• Restore logic now:
  • Collects unique judge IDs from team.reports.
  • For each reporting judge, requeues the team to the end only if: the submission exists for that judge/team, and is_scored === false.
  • Skips scored submissions (existing judged work is preserved).
  • Sets team.active = true.
  • Clears team.reports after successful processing.

Admin UI (/admin/teams)

• Added a team-level action button and helper text on reported teams
• Added confirmation prompt before execution

Behavior Notes

• Only judges who reported the team missing and still have an unscored submission are requeued.
• Non-reporting judges are unaffected.
• Scored submissions are not modified.

Fixes #466