feat: typing indicator orange dots, push-to-deafen hotkey, night light filter, message length counter

- #108: TypingIndicator reads lotusTerminal setting; applies var(--lt-accent-orange)
  to container so dots inherit via backgroundColor:currentColor
- #100: CallControls registers KeyM as push-to-deafen (e.code, e.repeat guard,
  ownerDocument.body iframe-safe editable check, [callEmbed] dep array)
- P5-5: nightLightEnabled/nightLightOpacity settings; position:fixed rgba(255,140,0)
  overlay inside JotaiProvider; Night Light tile + intensity slider (5–80%) in
  Settings → Appearance
- #101: RoomInput charCount state via Slate onChange + toPlainText; resets on
  room switch; displayed before send button when count > 0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/call/CallControls.tsx

@@ -196,6 +196,29 @@ export function CallControls({ callEmbed }: CallControlsProps) {
     // microphone intentionally read via microphoneRef — excluded from deps to avoid listener churn
   }, [pttMode, pttKey, callEmbed]);
 
+  useEffect(() => {
+    const isEditable = (el: HTMLElement): boolean => {
+      const tag = el.tagName;
+      if (tag === 'INPUT' || tag === 'TEXTAREA' || tag === 'SELECT') return true;
+      let node: HTMLElement | null = el;
+      while (node && node !== el.ownerDocument.body) {
+        if (node.contentEditable === 'true') return true;
+        if (node.contentEditable === 'false') return false;
+        node = node.parentElement;
+      }
+      return false;
+    };
+    const onKeyDown = (e: KeyboardEvent) => {
+      if (e.code !== 'KeyM') return;
+      if (e.repeat) return;
+      if (isEditable(e.target as HTMLElement)) return;
+      e.preventDefault();
+      callEmbed.control.toggleSound();
+    };
+    window.addEventListener('keydown', onKeyDown);
+    return () => window.removeEventListener('keydown', onKeyDown);
+  }, [callEmbed]);
+
   const [hangupState, hangup] = useAsyncCallback(
     useCallback(() => callEmbed.hangup(), [callEmbed]),
   );