fix: memory leaks — cleanup timers on unmount, tighten speech queue, fix isOwner reactivity

- FightViewer: track deferred speechSynthesis.cancel() timer, clear on unmount
- BotProfilePage: change isOwner from ref to computed for reactive login state
- sounds.ts: tighten speech queue depth cap from 3 to 2

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/game/sounds.ts

@@ -290,9 +290,9 @@ function speak(text: string, profileName: string, cancelPrevious: boolean = fals
   if (!voicesLoaded) loadVoices()
   // Chrome bug: speechSynthesis can get stuck. Nudge it.
   if (speechSynthesis.paused) speechSynthesis.resume()
-  // Only flush if queue is getting deep — allows voices to overlap naturally
+  // Flush if queue is getting deep — max 2 queued to prevent buildup
   if (cancelPrevious || (speechSynthesis.pending && speechSynthesis.speaking)) {
-    if (_speechQueueDepth > 3) {
+    if (_speechQueueDepth > 2) {
       speechSynthesis.cancel()
       _speechQueueDepth = 0
     }