feat: complete phase 5 -- error hardening, frontend, Docker, demo, docs

Backend:
- ConversationTracker: Protocol + PostgresConversationTracker for lifecycle tracking
- Error handler: ErrorCategory enum, classify_error(), with_retry() exponential backoff
- Wire PostgresAnalyticsRecorder + ConversationTracker into ws_handler
- Rate limiting (10 msg/10s per thread), edge case hardening
- Health endpoint GET /api/health, version 0.5.0
- Demo seed data script + sample OpenAPI spec

Frontend (all new):
- React Router with NavBar (Chat / Replay / Dashboard / Review)
- ReplayListPage + ReplayPage with ReplayTimeline component
- DashboardPage with MetricCard, range selector, zero-state
- ReviewPage for OpenAPI classification review
- ErrorBanner for WebSocket disconnect handling
- API client (api.ts) with typed fetch wrappers

Infrastructure:
- Frontend Dockerfile (multi-stage node -> nginx)
- nginx.conf with SPA routing + API/WS proxy
- docker-compose.yml with frontend service + healthchecks
- .env.example files (root + backend)

Documentation:
- README.md with quick start and architecture
- Agent configuration guide
- OpenAPI import guide
- Deployment guide
- Demo script

48 new tests, 449 total passing, 92.87% coverage

docker-compose.yml

@@ -28,12 +28,36 @@ services:
       ANTHROPIC_API_KEY: ${ANTHROPIC_API_KEY:-}
       OPENAI_API_KEY: ${OPENAI_API_KEY:-}
       GOOGLE_API_KEY: ${GOOGLE_API_KEY:-}
+      WEBHOOK_URL: ${WEBHOOK_URL:-}
+      SESSION_TTL_MINUTES: ${SESSION_TTL_MINUTES:-30}
+      INTERRUPT_TTL_MINUTES: ${INTERRUPT_TTL_MINUTES:-30}
+      TEMPLATE_NAME: ${TEMPLATE_NAME:-}
     depends_on:
       postgres:
         condition: service_healthy
-    volumes:
-      - ./backend:/app
-    command: uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload
+    healthcheck:
+      test: ["CMD-SHELL", "curl -f http://localhost:8000/api/health || exit 1"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+    networks:
+      - app_network
+
+  frontend:
+    build:
+      context: ./frontend
+      dockerfile: Dockerfile
+    ports:
+      - "80:80"
+    depends_on:
+      backend:
+        condition: service_healthy
+    networks:
+      - app_network
+
+networks:
+  app_network:
+    driver: bridge
 
 volumes:
   pgdata: