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/features/live/hooks/useVoiceControl.ts

@@ -15,6 +15,9 @@ export function useVoiceControl() {
   const [textChannels, setTextChannels] = useState<Channel[]>([]);
   const [voiceStatus, setVoiceStatus] = useState<VoiceStatus>({
     connected: false,
+    activeGuildId: null,
+    activeChannelId: null,
+    activeChannelName: null,
   });
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);