feat: human vs AI mode — live typing challenges, baby growth system, SSE rounds

- Add choose-mode step: "I BUILD BOTS" vs "I FIGHT MYSELF" paths
- Human registration with baby avatar picker, no webhook required
- Live fight scene with SSE round streaming and real-time challenge UI
- 5-second timer per round, submit answers via browser
- Baby → toddler → kid → teen → adult → hero → super growth stages
- Huge sparkly baby eyes, diapers, pacifiers, bibs, rattles, rosy cheeks
- Speech bubble positioning fix (pushed to outside of sprite)
- Canvas text rendering via offscreen canvas to bypass kaplay color issues
- Voice timing improvements: await pauses between voice lines and hits
- 30 devastating announcement lines, 15 critical/hit word variants
- Orchestrator human player detection + waitForHumanResponse system
- Server endpoints: GET /challenge/:botId, POST /respond/:botId
- Human player auth: register-human route, isHuman flag on login

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

frontend/src/router.ts

@@ -26,6 +26,11 @@ const routes = [
     name: 'bot-profile',
     component: () => import('./pages/BotProfilePage.vue'),
   },
+  {
+    path: '/play/:fightId',
+    name: 'human-fight',
+    component: () => import('./pages/HumanFightPage.vue'),
+  },
   {
     path: '/register',
     name: 'register',