Bring back 1-minute ready-status expiry with live per-player broadcasts

A player's own browser now starts a 60s timer the moment they check
"ready" (with a visible countdown) and proactively tells the server
when it's up via a new expire_ready action - idempotent, so it only
actually clears the status if the deadline has genuinely passed.
Everyone else finds out live through a Mercure player_ready broadcast
that now carries which player and their new ready/not-ready state
(previously the broadcast payload's `ready` flag was always false due
to a stale-variable bug, though nothing consumed it yet).

checkAllPlayersReady() still does the same expiry check server-side
and broadcasts on anyone else's request in the meantime, so a stalled
frontend timer doesn't leave a stale "ready" badge showing forever.

This only affects the pre-PLAYING ready phase: checkAllPlayersReady()
still flips the session to PLAYING and stops touching ready state the
instant everyone is simultaneously ready, so the earlier fix (a reload
should never send an already-started game back to the waiting room)
is unaffected.

Also fixed the ready checkbox itself: unchecking it submitted a POST
without `toggle_ready` in the body (unchecked checkboxes aren't sent),
so un-readying silently did nothing server-side. Added the standard
hidden-fallback-input pattern to fix it.

templates/game/waiting.html.twig

@@ -63,14 +63,18 @@
                     </div>
                 {% endif %}
                 <form method="post" class="mt-4">
+                    <input type="hidden" name="toggle_ready" value="0">
                     <div class="form-check form-switch mb-3">
-                        <input class="form-check-input" type="checkbox" id="toggle_ready" name="toggle_ready" onchange="this.form.submit()" {{ isReady ? 'checked' : '' }} {{ not app.user.verified ? 'disabled' : '' }}>
+                        <input class="form-check-input" type="checkbox" id="toggle_ready" name="toggle_ready" value="1" onchange="this.form.submit()" {{ isReady ? 'checked' : '' }} {{ not app.user.verified ? 'disabled' : '' }}>
                         <label class="form-check-label" for="toggle_ready">
                             <strong>I am ready to start!</strong>
                         </label>
                     </div>
                     <p class="text-muted small">
                         As soon as everyone has checked this box, the game starts automatically for everyone.
+                        {% if isReady %}
+                            Your ready status expires in <span id="ready-countdown">1:00</span> if not everyone else is ready by then.
+                        {% endif %}
                     </p>
                 </form>
 
@@ -82,9 +86,14 @@
     </div>
 </div>
 
+<form id="expire-ready-form" method="post" style="display:none">
+    <input type="hidden" name="expire_ready" value="1">
+</form>
+
 <div id="mercure-config"
      data-mercure-public-url="{{ mercure_public_url|e('html_attr') }}"
      data-topic="/game/hub/{{ session.id|e('html_attr') }}"
+     data-ready-at="{{ readyAt|e('html_attr') }}"
      style="display:none">
 </div>
 
@@ -92,6 +101,7 @@
     const config = document.getElementById('mercure-config');
     const publicUrl = config.dataset.mercurePublicUrl;
     const topic = config.dataset.topic;
+    const readyAt = config.dataset.readyAt;
 
     let reloading = false;
     const reloadOnce = (eventSource) => {
@@ -117,5 +127,37 @@
             }
         };
     }
+
+    // Our own ready status expires 60s after we set it - proactively tell the
+    // server as close to that deadline as possible, so the other players find
+    // out live instead of only whenever someone else's request happens to
+    // trigger the lazy check.
+    if (readyAt) {
+        const timeoutMs = 61000; // slightly more than the server-side 60s
+        const readyAtMs = readyAt * 1000;
+        const countdownEl = document.getElementById('ready-countdown');
+
+        const updateCountdown = () => {
+            const remaining = Math.max(0, Math.ceil((readyAtMs + timeoutMs - Date.now()) / 1000));
+            if (countdownEl) {
+                const m = Math.floor(remaining / 60);
+                const s = remaining % 60;
+                countdownEl.textContent = m + ':' + s.toString().padStart(2, '0');
+            }
+            return remaining;
+        };
+
+        const remaining = updateCountdown();
+        if (remaining <= 0) {
+            document.getElementById('expire-ready-form').submit();
+        } else {
+            const countdownInterval = setInterval(() => {
+                if (updateCountdown() <= 0) {
+                    clearInterval(countdownInterval);
+                    document.getElementById('expire-ready-form').submit();
+                }
+            }, 1000);
+        }
+    }
 </script>
 {% endblock %}