fix: IME layout, message dedup, animation order, and overlay input positioning

- ChatScreen: restructure to Box overlay layout so only input area
  rises with IME, messages stay fixed. Add opaque background to input
  area. Use reverseLayout with newest-first animation order.
- OverlayContent: remove all manual IME detection — system forces
  adjust=pan on VoiceInteractionSession windows, so manual padding
  caused double offset. Let system handle IME naturally.
- ChatRepositoryImpl: add messageRemovals flow to clean up wrapping
  stream_end/response when review/multi_message items arrive later.
  Track lastResponseId in both stream_end and response handlers.
- ChatViewModel/OverlayViewModel: fix dedup to check by message ID
  only. Sort descending (newest first). Observe messageRemovals.
- NavGraph: keep all tabs composed with graphicsLayer alpha toggle —
  prevents ChatScreen destruction and re-render on tab switch.
- CyreneVoiceInteractionSession: defer configureWindow via post()
  to override system softInputMode flags.
- AndroidManifest: set windowSoftInputMode=adjustNothing on main
  activity.
- Add WebSocketKeepAliveService for background connection persistence.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/src/main/java/top/yeij/cyrene/CyreneApplication.kt

@@ -89,7 +89,7 @@ class CyreneApplication : Application() {
     private fun getRepo(): ChatRepositoryImpl? {
         return try {
             GlobalContext.get().get()
-        } catch (_: Exception) {
+        } catch (_: Throwable) {
             null
         }
     }