fix: fight restart bug, mobile TTS, character sizing, bitcoin symbols

- Fix fight replay showing empty scene: validate rounds before playing,
  retry loading fight data up to 5 times when rounds are missing
- Add COOP/COEP headers to production server for SharedArrayBuffer
  (required by Kokoro TTS WASM threading on mobile)
- Add blob: to scriptSrc/workerSrc CSP for Web Worker support
- Fix mobile character cutoff: raise ground line to 0.82, add
  MOBILE_SCALE_CAP (0.55) so fighters never shrink too small
- Add ₿ bitcoin chest badge to all fighter sprites (scales with tier)
- Add sats coin stack on bot profile page proportional to satsWon
- Seed dev tournament with 8 mock bots on startup (dev mode only)

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

frontend/src/components/FightViewer.vue

@@ -322,6 +322,11 @@ async function replay() {
 
 async function _doReplay() {
   if (!props.fight.botA || !props.fight.botB) return
+  if (!props.fight.rounds || props.fight.rounds.length === 0) {
+    console.warn('[FightViewer] No rounds to play — skipping replay')
+    emit('replay-done')
+    return
+  }
   displayHpA.value = 100
   displayHpB.value = 100
   logItems.value = []