feat(teams): hide leave team button for submitted teams

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/hackathon/src/app/teams/[teamId]/page.tsx

@@ -480,6 +480,7 @@ const TeamDashboardPage: FC = (): ReactElement => {
                       </Button>
                     </Link>
                   )}
+                  {!team.has_submission && (
                     <Button
                       className="w-full bg-red-600 hover:bg-red-700 text-white"
                       onClick={() => setShowLeaveModal(true)}
@@ -487,6 +488,7 @@ const TeamDashboardPage: FC = (): ReactElement => {
                       <Icon icon="mdi:exit-run" className="inline-block mr-2" />
                       Leave Team
                     </Button>
+                  )}
                 </div>
               </div>
             )}