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/state/settings.ts

@@ -76,6 +76,9 @@ export interface Settings {
   callNoiseSuppression: boolean;
   pttMode: boolean;
   pttKey: string;
+
+  nightLightEnabled: boolean;
+  nightLightOpacity: number;
 }
 
 const defaultSettings: Settings = {
@@ -121,6 +124,9 @@ const defaultSettings: Settings = {
   callNoiseSuppression: true,
   pttMode: false,
   pttKey: 'Space',
+
+  nightLightEnabled: false,
+  nightLightOpacity: 30,
 };
 
 export const getSettings = (): Settings => {