Refactor WebSocket handlers and add ACK-based message flow

Consolidated coroutine scopes into `songListScope` and `timerScope` for better management across WebSocket routes. Introduced ACK (acknowledgment) handling for reliable message delivery with retries and timeouts. Updated session handling for multiple WebSocket routes to improve code maintainability and consistency.

common/src/main/kotlin/space/mori/chzzk_bot/common/events/TimerEvents.kt

@@ -5,7 +5,8 @@ enum class TimerType(var value: Int) {
     TIMER(1),
     REMOVE(2),
 
-    STREAM_OFF(50)
+    STREAM_OFF(50),
+    ACK(51)
 }
 
 class TimerEvent(