feat: dark mode fix, call wallpaper, setTheme error handling, Sentry filter

- CallEmbed: inject :root { color-scheme } into iframe so EC respects Cinny
  theme regardless of OS preference (fixes white background in dark mode)
- CallEmbed: store themeKind, update color-scheme CSS on live setTheme() calls
- CallEmbed: catch transport.send() rejection in setTheme() to prevent
  unhandled promise rejection when widget not ready yet (fixes REACT-8)
- CallEmbed: html + body both set to background:none so wallpaper shows through
- CallEmbedProvider: apply chatBackground wallpaper style to call embed
  container in full-view mode (not PiP) -- wallpapers carry over to calls
- useCallEmbed: pass themeKind through to CallEmbed constructor
- index.tsx: ignoreErrors: [Request timed out] to suppress matrixRTC
  heartbeat timeouts (REACT-9) from Sentry noise
- README: document 0.19.4, positioning fix, dark mode fix, wallpaper,
  millify Rolldown interop fix, Sentry noise filter

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

src/app/components/CallEmbedProvider.tsx

@@ -47,6 +47,10 @@ import { useMediaAuthentication } from '../hooks/useMediaAuthentication';
 import { mxcUrlToHttp, getMxIdLocalPart } from '../utils/matrix';
 import { RoomAvatar, RoomIcon } from './room-avatar';
 import { useRoomNavigate } from '../hooks/useRoomNavigate';
+import { getChatBg } from '../features/lotus/chatBackground';
+import { useTheme, ThemeKind } from '../hooks/useTheme';
+import { useSetting } from '../state/hooks/settings';
+import { settingsAtom } from '../state/settings';
 import { getStateEvent, getMemberDisplayName } from '../utils/room';
 import { StateEvent } from '../../types/matrix/room';
 import { getPowersLevelFromMatrixEvent } from '../hooks/usePowerLevels';
@@ -412,6 +416,14 @@ export function CallEmbedProvider({ children }: CallEmbedProviderProps) {
   const pipMode = callActive && !inCallRoom;
   const { navigateRoom } = useRoomNavigate();
 
+  const theme = useTheme();
+  const isDark = theme.kind === ThemeKind.Dark;
+  const [chatBackground] = useSetting(settingsAtom, 'chatBackground');
+  const wallpaperStyle = React.useMemo(
+    () => getChatBg(chatBackground, isDark),
+    [chatBackground, isDark],
+  );
+
   const pipDragRef = React.useRef<{
     startX: number;
     startY: number;
@@ -692,6 +704,7 @@ export function CallEmbedProvider({ children }: CallEmbedProviderProps) {
           left: 0,
           width: '100%',
           height: '50%',
+          ...(callVisible && !pipMode ? wallpaperStyle : {}),
         }}
         ref={callEmbedRef}
       >