style: apply ruff formatting to all backend files

backend/main.py

@@ -85,12 +85,14 @@ async def audit_middleware(request: Request, call_next):
     response = await call_next(request)
     if request.url.path.startswith("/api/") and request.method in ("POST", "PATCH", "PUT", "DELETE"):
         from auth import AUTH_ENABLED
+
         user = "anonymous"
         if AUTH_ENABLED:
             auth_header = request.headers.get("authorization", "")
             if auth_header.lower().startswith("bearer "):
                 try:
                     from jose import jwt
+
                     token = auth_header.split(" ", 1)[1]
                     claims = jwt.get_unverified_claims(token)
                     user = claims.get("sub", "unknown")
@@ -116,6 +118,7 @@ app.include_router(rules_router, prefix="/api")
 @app.get("/health")
 async def health_check():
     from database import db
+
     try:
         db.command("ping")
         return {"status": "ok", "database": "connected"}