fix(#338): Add rate limiting to orchestrator API

- Add @nestjs/throttler for rate limiting support
- Configure multiple throttle profiles: default (100/min), strict (10/min for spawn/kill), status (200/min for polling)
- Apply strict rate limits to spawn and kill endpoints to prevent DoS
- Apply higher rate limits to status/health endpoints for monitoring
- Add OrchestratorThrottlerGuard with X-Forwarded-For support for proxy setups
- Add unit tests for throttler guard

Refs #338

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/orchestrator/package.json

@@ -26,6 +26,7 @@
     "@nestjs/config": "^4.0.2",
     "@nestjs/core": "^11.1.12",
     "@nestjs/platform-express": "^11.1.12",
+    "@nestjs/throttler": "^6.5.0",
     "bullmq": "^5.67.2",
     "class-transformer": "^0.5.1",
     "class-validator": "^0.14.1",