fix(voice): restore voice features and apply critical optimizations

Voice Feature Restoration:
- Implemented full Redis pub/sub pipeline for real-time voice data
- Added VOICE_PCM and VOICE_ACTIVE_USER Redis channels
- Implemented EventBroadcaster.voicePcmData() and voiceActiveUser() methods
- Extended backend redis-bridge to subscribe to voice channels
- Updated backend WebSocket server for binary PCM broadcast
- Replaced globalThis PcmBroadcaster pattern with proper EventBroadcaster DI
- Fixed root cause: PcmBroadcaster functions were never initialized

Bug Fixes:
- Fixed prism-media version conflict (2.0.0-alpha.0 → 1.3.5)
- Fixed type inconsistency in commandHandler.ts (AudioPlayerStatus → string)

Critical Optimizations:
- P1.1: Fixed unbounded memory growth in aiAnalyzer (added LRU caching, max 10K entries)
- P1.2: Converted sync file I/O to async in audio hot paths (recorder, sessionRecording)
- P1.3: Replaced process.exit(1) with proper error handling (bootstrap, aiAnalysisWorker)

Code Quality:
- Removed unused logger field in EventBroadcaster
- Replaced console.* with structured logger.* calls (player, decoder)
- Fixed typos and removed commented debug code
- Added DatabaseError class for better error handling

Files Modified: 18 (discord-gateway: 14, backend: 3, root: 1)
Architecture: Discord → EventBroadcaster → Redis → Backend WebSocket → Frontend

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

services/backend/src/ws/broadcast.ts

@@ -11,6 +11,7 @@
 
 type BroadcastFn = (data: unknown) => void;
 type BroadcastRawFn = (type: string, data: unknown) => void;
+type BroadcastBinaryFn = (data: Buffer) => void;
 
 declare global {
   // biome-ignore lint/suspicious/noAssignInExpressions: intentional global broadcast registry
@@ -21,12 +22,14 @@ declare global {
         messageDeleted: BroadcastFn;
         attachmentUploaded: BroadcastFn;
         raw: BroadcastRawFn;
+        binary: BroadcastBinaryFn;
       }
     | undefined;
 }
 
 const noop: BroadcastFn = () => {};
 const noopRaw: BroadcastRawFn = () => {};
+const noopBinary: BroadcastBinaryFn = () => {};
 
 export const broadcastMessageCreated: BroadcastFn = (data) =>
   (globalThis.__broadcastFns?.messageCreated ?? noop)(data);
@@ -42,3 +45,6 @@ export const broadcastAttachmentUploaded: BroadcastFn = (data) =>
 
 export const broadcastRaw: BroadcastRawFn = (type, data) =>
   (globalThis.__broadcastFns?.raw ?? noopRaw)(type, data);
+
+export const broadcastBinary: BroadcastBinaryFn = (data) =>
+  (globalThis.__broadcastFns?.binary ?? noopBinary)(data);