chore: initial project setup with backend, frontend, Android app, and CI/CD

Add complete NexaMFA push MFA system with:
- FastAPI backend with PostgreSQL, Redis, OIDC provider, and Prometheus metrics
- React TypeScript admin console
- Android Kotlin/Jetpack Compose app with biometric authentication
- Docker Compose deployment configuration
- Gitea CI workflow for backend, frontend, and Android builds
- Environment configuration template with security settings
- Documentation for security model, deployment

backend/app/services/audit.py

@@ -0,0 +1,25 @@
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.audit import AuditLog
+
+
+async def audit(
+    session: AsyncSession,
+    action: str,
+    *,
+    actor: str | None = None,
+    target_type: str | None = None,
+    target_id: str | None = None,
+    ip_address: str | None = None,
+    metadata: dict | None = None,
+) -> None:
+    session.add(
+        AuditLog(
+            actor=actor,
+            action=action,
+            target_type=target_type,
+            target_id=target_id,
+            ip_address=ip_address,
+            metadata_json=metadata,
+        )
+    )