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

nginx/default.conf

@@ -0,0 +1,22 @@
+server {
+  listen 80;
+  server_name _;
+
+  location /api/ {
+    proxy_pass http://api:8000/api/;
+    proxy_set_header Host $host;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto $scheme;
+  }
+
+  location /healthz {
+    proxy_pass http://api:8000/healthz;
+  }
+
+  location / {
+    proxy_pass http://frontend:80;
+    proxy_set_header Host $host;
+  }
+}
+