fix: mobile menu overlay, speech bubble timing, TTS static file fallback

- Mobile nav menu now overlays content (absolute positioning) instead of
  pushing it down
- Speech bubbles stay visible for minimum 400ms even when TTS resolves
  instantly or fails
- kokoroPlayCached checks audio cache and loads static files even when
  Kokoro worker hasn't loaded — fixes TTS not playing on production
- CORS_ORIGIN env now supports comma-separated origins
- Rename "VIDEO REPLAY" to play icon + "REPLAY"

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

frontend/src/game/audio/voice.ts

@@ -788,10 +788,11 @@ export function playNarrationNow(text: string): Promise<void> {
 async function _playNowCore(text: string, profileName: string, rateOverride?: number): Promise<void> {
   if (getMasterMuted()) return
   const sfxGain = getSfxGain()
-  if (isKokoroReady() && sfxGain) {
+  // Try Kokoro (includes pre-generated static files from cache)
+  if (sfxGain) {
     const profile = voiceProfiles[profileName] || voiceProfiles.announcer
-    await kokoroPlayCached(text, profileName, sfxGain, profile.volume * VOICE_VOLUME_SCALE)
-    return
+    const played = await kokoroPlayCached(text, profileName, sfxGain, profile.volume * VOICE_VOLUME_SCALE)
+    if (played) return
   }
   // Fallback to Web Speech
   return _speakAsyncCore(text, profileName, rateOverride)