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/rbac.md

@@ -0,0 +1,13 @@
+# RBAC Concept
+
+Built-in roles:
+
+- Super Admin
+- Network Admin
+- Security Admin
+- Tenant Admin
+- Auditor
+- Read Only User
+
+Permissions are stored as strings and can use wildcard entries. Tenant and project scoping should be enforced in query services as the implementation matures.
+