fix: audio reliability — proper AudioContext resume, SFX destination, voice stability

- getSfxDest() helper centralizes SFX routing (replaces 38 inline calls)
- Await ensureAudioContext() before playing audio (fixes suspended context on prod)
- Chrome speechSynthesis pause bug workaround (periodic resume interval)
- Respect masterMuted on initial gain node creation
- Responsive overlay text sizes for small screens (text-2xl/5xl/7xl)
- Speech queue depth management with safety flush at depth > 3

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

frontend/src/pages/FightPage.vue

@@ -268,7 +268,7 @@ async function initLiveScene() {
 
   if (liveScene) {
     if (liveSoundOn.value) {
-      ensureAudioContext()
+      await ensureAudioContext()
       liveScene.startMusic()
     }
     announceDeepIntro()
@@ -517,9 +517,9 @@ async function handleFightEnd(data: any) {
   if (pollHandle) { clearInterval(pollHandle); pollHandle = null }
 }
 
-function toggleLiveSound() {
+async function toggleLiveSound() {
   liveSoundOn.value = !liveSoundOn.value
-  ensureAudioContext()
+  await ensureAudioContext()
   setMasterMute(!liveSoundOn.value)
 }
 
@@ -829,7 +829,7 @@ function stopAutoBattle() {
           <Transition name="announce">
             <div v-if="liveAnnouncementVisible"
                  class="absolute inset-0 flex items-center justify-center pointer-events-none z-20">
-              <p class="font-funky text-5xl sm:text-7xl tracking-widest uppercase announce-text"
+              <p class="font-funky text-2xl sm:text-5xl lg:text-7xl tracking-widest uppercase announce-text"
                  :style="{ color: liveAnnouncementColor, textShadow: `0 0 20px ${liveAnnouncementColor}, 0 0 40px ${liveAnnouncementColor}` }">
                 {{ liveAnnouncement }}
               </p>