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/redis-bridge.ts

@@ -25,8 +25,12 @@ const SUBSCRIPTIONS: ChannelMapping[] = [
     channel: "discord:analysis:queue_status",
     eventType: "analysis_queue_status",
   },
+  { channel: "discord:voice:active_user", eventType: "voice_active_user" },
 ];
 
+// Binary channels that need special handling (messageBuffer event)
+const BINARY_CHANNELS = ["discord:voice:pcm"];
+
 let subscriber: Redis | null = null;
 
 function createSubscriber(): Redis {
@@ -90,6 +94,41 @@ function handleSubscriptionMessage(channel: string, message: string): void {
   broadcastRaw(mapping.eventType, data);
 }
 
+/**
+ * Handle binary messages from Redis (e.g. voice PCM data).
+ * Expected format: 4-byte userId hash + PCM buffer
+ */
+function handleBinaryMessage(channel: Buffer, message: Buffer): void {
+  const channelStr = channel.toString();
+
+  if (channelStr === "discord:voice:pcm") {
+    if (message.length < 4) {
+      logger.warn(
+        { channel: channelStr, size: message.length },
+        "Received PCM message too short to contain userId",
+      );
+      return;
+    }
+
+    // First 4 bytes = userId hash, rest = PCM data
+    const userIdHash = message.readUInt32LE(0);
+    const pcmData = message.subarray(4);
+
+    logger.debug(
+      { channel: channelStr, userIdHash, pcmSize: pcmData.length },
+      "Broadcasting voice PCM data",
+    );
+
+    // Broadcast as binary: userId (4 bytes) + PCM data
+    broadcastRaw("voice_pcm", message);
+  } else {
+    logger.warn(
+      { channel: channelStr },
+      "Received binary message for unmapped channel",
+    );
+  }
+}
+
 export async function startRedisBridge(): Promise<void> {
   if (!config.REDIS_URL && !config.REDIS_HOST) {
     logger.info("Redis not configured, skipping Redis bridge");
@@ -116,6 +155,7 @@ export async function startRedisBridge(): Promise<void> {
     });
 
     subscriber.on("message", handleSubscriptionMessage);
+    subscriber.on("messageBuffer", handleBinaryMessage);
 
     await subscriber.ping();
     logger.info("Redis ping OK");
@@ -124,6 +164,11 @@ export async function startRedisBridge(): Promise<void> {
     await subscriber.subscribe(...channels);
     logger.info({ channels }, "Subscribed to Redis channels");
 
+    if (BINARY_CHANNELS.length > 0) {
+      await subscriber.subscribe(...BINARY_CHANNELS);
+      logger.info({ channels: BINARY_CHANNELS }, "Subscribed to binary Redis channels");
+    }
+
     logger.info("Redis bridge started");
   } catch (err) {
     logger.error({ err }, "Failed to start Redis bridge");