feat: implement all real backend endpoints, Redis pub/sub bridge, and gateway command handler

Backend (real implementations, no more stubs):
- Redis pub/sub bridge: subscribes to discord-gateway events (message/attachment/voice) and broadcasts to WS clients
- Redis command channel: backend publishes voice/media commands, discord-gateway executes and replies
- Voice service: connectVoice/disconnectVoice/getVoiceStatus via Redis commands with graceful fallback
- Media service: queue/skip/stop/volume via Redis commands, reads status from Redis cache
- Messages repository: ALL 7 methods now use real PostgreSQL queries (findMany, findById, findByChannel, create, update, delete, getAttachmentsByChannel)
- Analytics: period returns {start,end} epoch millis, overview includes hourly/topics/top_users, worst_flags as string[]
- Health check: actually queries SELECT 1 against database
- VoiceStatus type fixed: {connected, activeGuildId, activeChannelId, activeChannelName}
- Guild type: includes icon: string | null
- asyncHandler: accepts Promise<unknown> instead of Promise<void>

Discord Gateway:
- CommandHandler: subscribes to 'backend:command' Redis channel, executes voice/media commands, publishes replies
- Publishes voice:status and media:status to Redis for backend caching
- Shutdown handler updated to close command handler

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/backend/src/modules/voice/voice.controller.ts

@@ -7,7 +7,7 @@ import {
 } from "./voice.service.js";
 
 export async function handleGetVoiceStatus(_req: Request, res: Response) {
-  const status = getVoiceStatus();
+  const status = await getVoiceStatus();
   res.json(status);
 }