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/pages/App.tsx

@@ -1,6 +1,6 @@
 import React from 'react';
 import * as Sentry from '@sentry/react';
-import { Provider as JotaiProvider } from 'jotai';
+import { Provider as JotaiProvider, useAtomValue } from 'jotai';
 import { OverlayContainerProvider, PopOutContainerProvider, TooltipContainerProvider } from 'folds';
 import { RouterProvider } from 'react-router-dom';
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
@@ -13,6 +13,24 @@ import { FeatureCheck } from './FeatureCheck';
 import { createRouter } from './Router';
 import { ScreenSizeProvider, useScreenSize } from '../hooks/useScreenSize';
 import { useCompositionEndTracking } from '../hooks/useComposingCheck';
+import { settingsAtom } from '../state/settings';
+
+function NightLightOverlay() {
+  const settings = useAtomValue(settingsAtom);
+  if (!settings.nightLightEnabled) return null;
+  return (
+    <div
+      aria-hidden="true"
+      style={{
+        position: 'fixed',
+        inset: 0,
+        pointerEvents: 'none',
+        zIndex: 9998,
+        backgroundColor: `rgba(255, 140, 0, ${(settings.nightLightOpacity ?? 30) / 100})`,
+      }}
+    />
+  );
+}
 
 const queryClient = new QueryClient();
 
@@ -76,6 +94,7 @@ function App() {
                       <QueryClientProvider client={queryClient}>
                         <JotaiProvider>
                           <RouterProvider router={createRouter(clientConfig, screenSize)} />
+                          <NightLightOverlay />
                         </JotaiProvider>
                         <ReactQueryDevtools initialIsOpen={false} />
                       </QueryClientProvider>