fix: add async/await to timer event handlers for sound

frontend/src/App.svelte

@@ -101,17 +101,17 @@
     timerState = state
   }
 
-  function handleWarning(state) {
+  async function handleWarning(state) {
     timerState = state
     if (settings?.soundEnabled) {
-      playSound('warning')
+      await playSound('warning')
     }
   }
 
-  function handleTimeUp(state) {
+  async function handleTimeUp(state) {
     timerState = state
     if (settings?.soundEnabled) {
-      playSound('timeup')
+      await playSound('timeup')
     }
   }
 
@@ -119,11 +119,11 @@
     timerState = state
   }
 
-  function handleMeetingEnded(state) {
+  async function handleMeetingEnded(state) {
     timerState = state
     meetingActive = false
     if (settings?.soundEnabled) {
-      playSound('meeting_end')
+      await playSound('meeting_end')
     }
   }