Fix code formatting and linting issues

- Auto-format all Python files with black and isort
- Remove unused imports with autoflake
- Fix flake8 issues (missing newlines, blank lines, etc.)
- Fix nonlocal/global scope issues in main.py
- Fix security.py import order (E402)
- Remove f-string without placeholders
- Add nosec comment for intentional exception handling
- Fix test imports to match refactored DMARCParser API

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

backend/app/api/api_v1/endpoints/health.py

@@ -1,9 +1,9 @@
+from app.api.api_v1.endpoints.setup import setup_status
 from fastapi import APIRouter
 
-from app.api.api_v1.endpoints.setup import setup_status
-
 router = APIRouter()
 
+
 @router.get("/health", status_code=200)
 async def health_check():
     """
@@ -14,5 +14,5 @@ async def health_check():
         "status": "ok",
         "version": "0.1.0",
         "service": "dmarq",
-        "is_setup_complete": setup_status["is_setup_complete"]
-    }
+        "is_setup_complete": setup_status["is_setup_complete"],
+    }