feat(system): implement graceful shutdown and expand websocket events

Improve system reliability and real-time capabilities by implementing a robust lifecycle management system and adding new broadcast events for attachments and voice recordings.

- Implement asynchronous graceful shutdown in backend to close HTTP, WebSocket, Redis, and database connections.
- Add new WebSocket broadcast events: `attachment_created`, `voice_recording_started`, `voice_recording_stopped`, `voice_recording_uploaded`, and `analysis_queue_status`.
- Refactor media status handling to use boolean `playing` state instead of string-based status.
- Centralize `PageResult` and `VoiceRecording` types to improve consistency between frontend and backend.
- Update frontend API client to include `listRecordings` and handle new WebSocket event types.
- Fix type mismatches in voice command handling and media status reporting.

services/frontend/src/App.tsx

@@ -88,6 +88,10 @@ export default function App() {
       messages
         .fetchMessages(monitorGuildId || undefined)
         .catch(() => undefined),
+    onAttachmentCreated: () =>
+      messages
+        .fetchMessages(monitorGuildId || undefined)
+        .catch(() => undefined),
     onMediaState: (state) => media.setMediaState(state as MediaState),
     onVoiceRecordingUploaded: (d) =>
       window.dispatchEvent(