fix(calls): release a push-to-talk hold after 5 minutes (#136)

Elbow-on-the-keyboard guard: a PTT hold longer than 5 min (fixed, not a
setting) is released exactly like a keyup — pttActive off, mic muted — with a
toast 'Push to talk released after 5 minutes — press the key again to keep
talking.' A fresh press re-engages normally. One watchdog shared by the DOM
path and the desktop-global hotkey path; keydown auto-repeat no longer
restarts anything; non-PTT mode, deafen and the mic button are untouched.
Helper unit-tested with fake timers; verified headless with Playwright's clock:
held → still open at +4 min → released + toast at +5 min → re-press works.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/utils/pttHoldWatchdog.ts

@@ -0,0 +1,40 @@
+/**
+ * [Gitea #136] Elbow-on-the-keyboard guard for push-to-talk: a hold longer
+ * than `maxMs` is released as if the key came up. `arm()` on press, `disarm()`
+ * on release (a genuine release + re-press restarts the clock). Timers are
+ * injectable for tests.
+ */
+export const PTT_MAX_HOLD_MS = 5 * 60 * 1000;
+
+type Timers = {
+  setTimeout: (fn: () => void, ms: number) => unknown;
+  clearTimeout: (handle: unknown) => void;
+};
+
+const realTimers: Timers = {
+  setTimeout: (fn, ms) => setTimeout(fn, ms),
+  clearTimeout: (h) => clearTimeout(h as ReturnType<typeof setTimeout>),
+};
+
+export const createPttHoldWatchdog = (
+  onExpire: () => void,
+  maxMs = PTT_MAX_HOLD_MS,
+  timers: Timers = realTimers,
+) => {
+  let handle: unknown;
+  const disarm = () => {
+    if (handle !== undefined) timers.clearTimeout(handle);
+    handle = undefined;
+  };
+  return {
+    arm: () => {
+      disarm();
+      handle = timers.setTimeout(() => {
+        handle = undefined;
+        onExpire();
+      }, maxMs);
+    },
+    disarm,
+    armed: () => handle !== undefined,
+  };
+};