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

.gitlab-ci.yml

@@ -0,0 +1,50 @@
+stages:
+  - test
+  - build
+  - security
+  - release
+
+backend:
+  image: python:3.12-slim
+  stage: test
+  script:
+    - cd backend
+    - pip install ".[dev]"
+    - ruff check .
+    - pytest
+
+frontend:
+  image: node:22-alpine
+  stage: test
+  script:
+    - cd frontend
+    - npm install
+    - npm test
+    - npm run build
+
+docker-build:
+  image: docker:27
+  stage: build
+  services:
+    - docker:27-dind
+  script:
+    - docker build -t nexafabric-api:$CI_COMMIT_SHA backend
+    - docker build -t nexafabric-frontend:$CI_COMMIT_SHA frontend
+
+security-scan:
+  image: aquasec/trivy:latest
+  stage: security
+  script:
+    - trivy fs --exit-code 0 --severity HIGH,CRITICAL .
+
+openapi:
+  image: python:3.12-slim
+  stage: release
+  script:
+    - cd backend
+    - pip install ".[dev]"
+    - python -c "import json; from app.main import app; print(json.dumps(app.openapi()))" > ../openapi.json
+  artifacts:
+    paths:
+      - openapi.json
+