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/components/FightViewer.vue

@@ -46,6 +46,7 @@ const canvasContainer = ref<HTMLElement>()
 const logEl = ref<HTMLElement>()
 let scene: FightSceneController | null = null
 const sceneReady = ref(false)
+let cleanupTimerHandle: ReturnType<typeof setTimeout> | null = null
 
 const isReplaying = ref(false)
 const displayHpA = ref(100)
@@ -98,6 +99,8 @@ onUnmounted(() => {
   stopAllAudio()
   sceneReady.value = false
   if (scene) { scene.destroy(); scene = null }
+  if (cleanupTimerHandle) { clearTimeout(cleanupTimerHandle); cleanupTimerHandle = null }
+  if (typeof speechSynthesis !== 'undefined') speechSynthesis.cancel()
 })
 
 async function initScene() {
@@ -398,8 +401,10 @@ async function replay() {
   }
 
   // Kill any remaining queued speech — fight is over
-  setTimeout(() => {
+  if (cleanupTimerHandle) clearTimeout(cleanupTimerHandle)
+  cleanupTimerHandle = setTimeout(() => {
     if (typeof speechSynthesis !== 'undefined') speechSynthesis.cancel()
+    cleanupTimerHandle = null
   }, 3000)
 
   isReplaying.value = false