fix: CI biome errors + enhanced GUILD_CREATE/READY voice_states diagnostic

- live-speaker.ts: unused var [id] in clearAllSpeakers → [_]
- migrate.ts: useTemplate string concat → template literal
- streamWatchReceiver: remove unused watchKey param from closeCurrentSegment
- videoRecorder: log all raw WS event types + READY sessions.voice + broadcaster_user_ids

services/backend/src/modules/voice/live-speaker.ts

@@ -99,7 +99,7 @@ export function getSpeakingSpeakers(): LiveSpeaker[] {
  * snapshot doesn't carry ghost speakers.
  */
 export function clearAllSpeakers(): void {
-  for (const [id, s] of speakers) {
+  for (const [, s] of speakers) {
     s.speaking = false;
   }
   purgeStale();