Wire up decode puzzle chain and lock terminal on file removal

Connects the previously-disconnected /decode command to per-player
messages: player 1 unlocks sudo for everyone, player 2 unlocks a scan
command that reveals which files the AI virus has locked, player 3
learns those files should be removed.

Also adds a retaliation mechanic: successfully removing a file locks
the player's terminal. The AI virus locks it out in red immediately;
the mainframe reveals a 12-character recovery code in green after 30
seconds, which can be submitted via /unlock to restore access early,
otherwise the terminal auto-recovers after 45 seconds.

templates/game/index.html.twig

@@ -21,12 +21,21 @@
              data-api-check-finished-url="{{ path('game_api_check_finished', {session: session.id})|e('html_attr') }}"
              data-lost-url="{{ path('game_lost', {session: session.id})|e('html_attr') }}"
              data-screen="{{ screen|e('html_attr') }}"
+             {% if lock %}
+             data-lock-locked-at="{{ lock.lockedAt }}"
+             data-lock-reveal-at="{{ lock.revealAt }}"
+             data-lock-unlock-at="{{ lock.unlockAt }}"
+             {% endif %}
              style="display:none">
         </div>
 
         <div id="game-timer" data-end-time="{{ session.timer }}">
             --:--:--
         </div>
+        <div id="lock-banner" style="display:none">
+            <div id="lock-banner-text">AI VIRUS: SYSTEM LOCKED</div>
+            <div id="lock-countdown">--</div>
+        </div>
         <div id="message-container">
 
         </div>