fix: early name validation, fighter glow, reduced visual noise

- Add /api/auth/check-name endpoint for early name availability check
- JoinBoutPage checks name availability at naming step (not after webhook)
- FightCardPage: replace poster containers with circular glow behind sprites
- Reduce synthwave grid and CRT overlay opacity for cleaner backgrounds
- BotProfilePage: webhook management, owner-only fields
- useNostr: normalize bot data, guard auto-restore, clearAllState helper
- bots.ts: expose owner-only webhook info on stats endpoint

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

frontend/src/style.css

@@ -39,8 +39,8 @@
 /* Synthwave grid background */
 .synthwave-grid {
   background-image:
-    linear-gradient(rgba(184, 61, 255, 0.06) 1px, transparent 1px),
-    linear-gradient(90deg, rgba(184, 61, 255, 0.06) 1px, transparent 1px);
+    linear-gradient(rgba(184, 61, 255, 0.025) 1px, transparent 1px),
+    linear-gradient(90deg, rgba(184, 61, 255, 0.025) 1px, transparent 1px);
   background-size: 40px 40px;
 }
 
@@ -48,8 +48,8 @@
 .crt-overlay {
   background: repeating-linear-gradient(
     0deg,
-    rgba(0, 0, 0, 0.12) 0px,
-    rgba(0, 0, 0, 0.12) 1px,
+    rgba(0, 0, 0, 0.04) 0px,
+    rgba(0, 0, 0, 0.04) 1px,
     transparent 1px,
     transparent 3px
   );