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

scripts/backup.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env sh
+set -eu
+
+mkdir -p backups
+docker compose exec -T postgres pg_dump -U nexafabric nexafabric >"backups/nexafabric-$(date +%Y%m%d-%H%M%S).sql"
+