feat: quick emoji reactions on hover, in-app notification toasts, mention pulse audit

P5-17: MessageQuickReactions moved from 3-dots menu to hover toolbar;
shows 5 recent emoji directly on hover. Clicking a quick-reaction also
closes any open emoji picker (setEmojiBoardAnchor). Line separator
removed from component.

P5-7: LotusToastContainer slides in from bottom-right when window is
focused — replaces OS notification for in-focus events. Correct room
path (DM vs home) derived from mDirectAtom. Invite toast routes to
inbox. 4s auto-dismiss. Full TDS styling via CSS custom properties.

P5-8: Confirmed already implemented upstream (MentionHighlightPulse,
0.6s scale+glow, one-shot, prefers-reduced-motion). Marked complete.

Code-review fixes: toast navigation used nonexistent /room/ route;
emoji picker stayed open after toolbar quick-reaction.

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

src/app/pages/App.tsx

@@ -14,6 +14,7 @@ import { createRouter } from './Router';
 import { ScreenSizeProvider, useScreenSize } from '../hooks/useScreenSize';
 import { useCompositionEndTracking } from '../hooks/useComposingCheck';
 import { settingsAtom } from '../state/settings';
+import { LotusToastContainer } from '../features/toast/LotusToastContainer';
 
 function NightLightOverlay() {
   const settings = useAtomValue(settingsAtom);
@@ -95,6 +96,7 @@ function App() {
                         <JotaiProvider>
                           <RouterProvider router={createRouter(clientConfig, screenSize)} />
                           <NightLightOverlay />
+                          <LotusToastContainer />
                         </JotaiProvider>
                         <ReactQueryDevtools initialIsOpen={false} />
                       </QueryClientProvider>