feat: SSE live fight spectating with spectator count

Enable real-time fight spectating for all live fights (not just human
fights). Multiple spectators can watch simultaneously via SSE. Spectator
count is tracked per-fight and broadcast with every SSE event.

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

frontend/src/router.ts

@@ -61,6 +61,11 @@ const routes = [
     name: 'docs',
     component: () => import('./pages/DocsPage.vue'),
   },
+  {
+    path: '/soundboard',
+    name: 'soundboard',
+    component: () => import('./pages/SoundboardPage.vue'),
+  },
 ]
 
 export const router = createRouter({