feat(docker): add multi-container cluster deployment with CLI management

Add comprehensive Docker cluster orchestration with horizontal scaling support.

CLI Commands:
- crwl server start/stop/restart/status/scale/logs
- Auto-detection: Single (N=1) → Swarm (N>1) → Compose (N>1 fallback)
- Support for 1-100 container replicas with zero-downtime scaling

Infrastructure:
- Nginx load balancing (round-robin API, sticky sessions monitoring)
- Redis-based container discovery via heartbeats (30s interval)
- Real-time monitoring dashboard with cluster-wide visibility
- WebSocket aggregation from all containers

Security & Stability Fixes (12 critical issues):
- Add timeout protection to browser pool locks (prevent deadlocks)
- Implement Redis retry logic with exponential backoff
- Add container ID validation (prevent Redis key injection)
- Add CLI input sanitization (prevent shell injection)
- Add file locking for state management (prevent corruption)
- Fix WebSocket resource leaks and connection cleanup
- Add graceful degradation and circuit breakers

Configuration:
- RedisTTLConfig dataclass with environment variable support
- Template-based docker-compose.yml and nginx.conf generation
- Comprehensive error handling with actionable messages

Documentation:
- AGENT.md: Complete DevOps context for AI assistants
- MULTI_CONTAINER_ARCHITECTURE.md: Technical architecture guide
- Reorganized docs into deploy/docker/docs/

deploy/docker/server.py

@@ -200,7 +200,11 @@ async def root():
     return RedirectResponse("/playground")
 
 # ─────────────────── infra / middleware  ─────────────────────
-redis = aioredis.from_url(config["redis"].get("uri", "redis://localhost"))
+# Build Redis URL from environment or config
+redis_host = os.getenv("REDIS_HOST", config["redis"].get("host", "localhost"))
+redis_port = os.getenv("REDIS_PORT", config["redis"].get("port", 6379))
+redis_url = config["redis"].get("uri") or f"redis://{redis_host}:{redis_port}"
+redis = aioredis.from_url(redis_url)
 
 limiter = Limiter(
     key_func=get_remote_address,