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/pages/FightPage.vue

@@ -357,7 +357,12 @@ async function handleFightEnd(data: any) {
   if (liveScene) { liveScene.destroy(); liveScene = null }
   liveSceneReady.value = false
 
-  await loadFight()
+  // Retry loading until rounds are populated (server may still be persisting)
+  for (let attempt = 0; attempt < 5; attempt++) {
+    await loadFight()
+    if (fight.value?.rounds?.length) break
+    await new Promise(r => setTimeout(r, 800))
+  }
   isLive.value = false
   disconnectSSE()
   stopHumanPolling()