refactor(core): introduce EventBus and refactor store infrastructure

- Add EventBus for decoupled event-driven communication between services
- Add EventSubscriber component for centralized event handling
- Add requestDedupe utility for shared request deduplication
- Refactor api/wsService to use eventBus instead of direct router navigation
- Extract MessageMapper.toCachedMessages for consistent message mapping
- Remove deprecated BaseManager and CacheBus classes
- Improve @mention rendering with memberMap support in segment rendering
- Update hooks to use useRef instead of useState for fetch tracking

app/_layout.tsx

@@ -12,6 +12,7 @@ import * as SystemUI from 'expo-system-ui';
 import { registerNotificationPresentationHandler } from '../src/services/notificationPreferences';
 import { api } from '../src/services/api';
 import { wsService } from '../src/services/wsService';
+import { EventSubscriber } from '../src/infrastructure/EventSubscriber';
 import {
   ThemeBootstrap,
   useAppColors,
@@ -185,15 +186,11 @@ function ThemedStack() {
   const colors = useAppColors();
   const resolved = useResolvedColorScheme();
 
-  useEffect(() => {
-    api.setExpoRouter(router);
-    wsService.setRouter(router);
-  }, [router]);
-
   return (
     <>
       <StatusBar style={resolved === 'dark' ? 'light' : 'dark'} />
       <SystemChrome />
+      <EventSubscriber />
       <SessionGate>
         <NotificationBootstrap />
         <APKUpdateBootstrap />