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

backend/app/core/security.py

@@ -0,0 +1,52 @@
+from datetime import datetime, timedelta, timezone
+from typing import Any
+
+from jose import jwt
+from passlib.context import CryptContext
+
+from app.core.config import get_settings
+
+
+pwd_context = CryptContext(schemes=["argon2"], deprecated="auto")
+
+
+def hash_password(password: str) -> str:
+    return pwd_context.hash(password)
+
+
+def verify_password(password: str, password_hash: str) -> bool:
+    return pwd_context.verify(password, password_hash)
+
+
+def create_token(subject: str, token_type: str, expires_delta: timedelta, claims: dict[str, Any] | None = None) -> str:
+    settings = get_settings()
+    now = datetime.now(timezone.utc)
+    payload: dict[str, Any] = {
+        "sub": subject,
+        "typ": token_type,
+        "iat": now,
+        "exp": now + expires_delta,
+    }
+    if claims:
+        payload.update(claims)
+    return jwt.encode(payload, settings.jwt_secret, algorithm="HS256")
+
+
+def create_access_token(subject: str, permissions: list[str]) -> str:
+    settings = get_settings()
+    return create_token(
+        subject,
+        "access",
+        timedelta(minutes=settings.jwt_access_token_minutes),
+        {"permissions": permissions},
+    )
+
+
+def create_refresh_token(subject: str) -> str:
+    settings = get_settings()
+    return create_token(subject, "refresh", timedelta(days=settings.jwt_refresh_token_days))
+
+
+def decode_token(token: str) -> dict[str, Any]:
+    return jwt.decode(token, get_settings().jwt_secret, algorithms=["HS256"])
+