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/firewall-orchestration.md

@@ -0,0 +1,16 @@
+# Firewall Orchestration
+
+NexaFabric must never overwrite productive firewall state without operator intent.
+
+Required lifecycle:
+
+1. Compile policy.
+2. Generate preview.
+3. Detect warnings and conflicts.
+4. Persist audit record.
+5. Require approval for apply.
+6. Acquire a cluster/node lock.
+7. Apply provider-specific rules.
+8. Detect drift after apply.
+9. Support rollback using previous compiled versions.
+