feat(discord-gateway): implement voice & push improvements

- Voice disconnect broadcast on stopRecording
- Multi-guild voice support (VoiceController Map<guildId>)
- Session finalization + auto-enqueue muxer job
- Recordings API: duration field, channelId/userId filters
- Transmitter Redis connection reuse (shared conn)
- FFmpeg stderr memory cap (4KB limit)
- 10 new Redis event channels + Redis bridge subscriptions
- New DB tables: message_reactions, message_edits
- Webhook notification module
- Gateway metrics / Prometheus endpoint
- Multi-guild message capture (MONITOR_GUILD_IDS array)
- Thread tracking, presence, channel topic, guild member events
- Edit history snapshot on message update
- Muxer audio post-processing worker

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

services/discord-gateway/src/modules/command-handler/handler-registry.ts

@@ -9,6 +9,7 @@ import {
   COMMAND_VOICE_CHANNELS,
   COMMAND_VOICE_CONNECT,
   COMMAND_VOICE_DISCONNECT,
+  COMMAND_VOICE_DISCONNECT_GUILD,
   COMMAND_VOICE_TRANSMIT_START,
   COMMAND_VOICE_TRANSMIT_STOP,
   type CommandMessage,
@@ -46,6 +47,9 @@ export function createHandlerRegistry(
   registry.set(COMMAND_VOICE_DISCONNECT, (cmd) =>
     voiceHandler.handleVoiceDisconnect(cmd),
   );
+  registry.set(COMMAND_VOICE_DISCONNECT_GUILD, (cmd) =>
+    voiceHandler.handleVoiceDisconnectGuild(cmd),
+  );
   registry.set(COMMAND_VOICE_CHANNELS, (cmd) =>
     voiceHandler.handleVoiceChannels(cmd),
   );