chore: initial project setup with backend, frontend, CI/CD, and documentation

Add complete NexaFabric project structure including:
- FastAPI backend with SQLAlchemy models, JWT auth, RBAC, audit logging, and provider interfaces
- React + TypeScript frontend with Vite, Tailwind CSS, TanStack Query, and Zustand
- Docker Compose configuration for PostgreSQL, Redis, API, worker, frontend, and nginx
- GitHub Actions and GitLab CI workflows for testing, linting, building, and security scanning
- Environment

docs/api-examples.md

@@ -0,0 +1,24 @@
+# API Examples
+
+Login:
+
+```bash
+curl -X POST http://localhost:8080/api/v1/auth/login \
+  -H 'Content-Type: application/json' \
+  -d '{"email":"admin@nexafabric.local","password":"ChangeMe_UseEnvInstead"}'
+```
+
+List clusters:
+
+```bash
+curl http://localhost:8080/api/v1/clusters \
+  -H "Authorization: Bearer $TOKEN"
+```
+
+Generate firewall preview:
+
+```bash
+curl -X POST http://localhost:8080/api/v1/firewall/preview/$POLICY_ID \
+  -H "Authorization: Bearer $TOKEN"
+```
+