Auto-trigger locked-files restoration exactly at the 60s deadline

Previously the restore check only ran lazily on a player's next
message, so files could stay wrongly-removed for an arbitrary amount
of time after the window expired. The frontend now schedules a
setTimeout (using the server-provided deadline, mirroring the terminal
lock's reveal timer) that pings the backend right at the deadline so
the check runs promptly regardless of player activity. Restored via
data-files-removal-deadline on page load too, so a refresh mid-window
doesn't lose the timer.

src/Game/Controller/GameController.php

@@ -160,12 +160,14 @@ final class GameController extends AbstractController
         $screen = $player ? $player->getScreen() : 0;
         $session_id = $session->getId();
         $lock = $player ? $gameResponseService->getPublicLockState($player) : null;
+        $filesRemovalDeadline = $gameResponseService->getPublicLockedFilesDeadline($session);
 
         return $this->render('game/index.html.twig', [
             'session' => $session,
             'screen' => $screen,
             'session_id' => $session_id,
             'lock' => $lock,
+            'filesRemovalDeadline' => $filesRemovalDeadline,
         ]);
     }