refactor: remove voice, recording, and music/media features (gateway + backend)

- Gateway: delete voice-recording/, voice-pcm-ws/, voice/video/media handlers,
  vendor/discord-voice-fork/, voice DB repos, 2 voice migrations
- Gateway: cut voice wiring from bootstrap/shutdown/commandHandler/handler-registry,
  eventBroadcaster/eventTypes, redis-channels, moderation-types, message-capture,
  config keys, and deps (@discordjs/voice, opus, libsodium, prism-media, davey)
- Backend: delete voice/, recordings/, media/ modules + @discordjs/voice dep
- Backend: cut voice/media/recordings oRPC routers, WS gateway-PCM auth + voice
  handlers, Redis bridge voice aggregation, redis-channels voice/media constants,
  config keys, moderation-types voice items, e2e voice/recordings suites
- Keep voice DB tables (destructive migration avoided); chatbot voiceRecordings
  tool + dashboard count remain as read-only historical data access

services/discord-gateway/drizzle/migrations/meta/_journal.json

@@ -79,13 +79,6 @@
       "tag": "0010_add_reactions_and_edit_history",
       "breakpoints": true
     },
-    {
-      "idx": 11,
-      "version": "7",
-      "when": 1785600000000,
-      "tag": "0011_add_voice_transcription",
-      "breakpoints": true
-    },
     {
       "idx": 12,
       "version": "7",
@@ -141,13 +134,6 @@
       "when": 1787830000000,
       "tag": "0019_rename_server_name_to_server_nick",
       "breakpoints": true
-    },
-    {
-      "idx": 20,
-      "version": "7",
-      "when": 1787860000000,
-      "tag": "0020_add_voice_auto_reconnect",
-      "breakpoints": true
     }
   ]
 }