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/shared/api/client.ts

@@ -1,6 +1,6 @@
 // ─── Shared HTTP client — all API endpoints in one file ──────────────────────
 
-import type { MessageRecord } from "@bete/shared";
+import type { MessageRecord, PageResult } from "@bete/shared";
 
 const BE_API_URL = import.meta.env.VITE_BE_API_URL || "http://localhost:3001";
 const BE_WS_URL = import.meta.env.VITE_BE_WS_URL || "ws://localhost:3001";
@@ -54,12 +54,7 @@ export function getAPIURL(): string {
 
 // ─── Types ───────────────────────────────────────────────────────────────────
 
-export interface PageResult<T> {
-  data: T[];
-  nextCursor: string | null;
-}
-
-export type { MessageRecord };
+export type { MessageRecord, PageResult };
 
 export interface Guild {
   id: string;
@@ -76,9 +71,9 @@ export interface Channel {
 
 export interface VoiceStatus {
   connected: boolean;
-  activeGuildId?: string | null;
-  activeChannelId?: string | null;
-  activeChannelName?: string | null;
+  activeGuildId: string | null;
+  activeChannelId: string | null;
+  activeChannelName: string | null;
 }
 
 export interface ActiveSpeaker {
@@ -237,6 +232,29 @@ export function setMediaVolume(volume: number): Promise<MediaState> {
   });
 }
 
+// ─── Recordings ──────────────────────────────────────────────────────────────
+
+export interface VoiceRecording {
+  id: string;
+  user_id: string;
+  username: string;
+  avatar_url: string | null;
+  guild_id: string | null;
+  channel_id: string | null;
+  channel_name: string | null;
+  filename: string;
+  size_bytes: number;
+  download_url: string | null;
+  upload_status: "pending" | "uploaded" | "failed";
+  upload_error: string | null;
+  created_at: number;
+  uploaded_at: number | null;
+}
+
+export function listRecordings(limit = 50): Promise<VoiceRecording[]> {
+  return request<VoiceRecording[]>(`/api/recordings?limit=${limit}`);
+}
+
 // ─── Auth ────────────────────────────────────────────────────────────────────
 
 export function login(password: string): Promise<{ ok: boolean }> {