style: fix all flake8 linter errors across app/ directory

- Run Black formatter and isort on all app/ files
- Remove unused imports (F401) across multiple files
- Add # noqa: F401 for intentional re-exports in celery_worker.py,
  tasks/__init__.py, utils.py, frontend.py, views/base.py
- Fix f-strings without placeholders (F541) in azure.py, notification.py,
  check_credentials.py, upload_to_onedrive.py, settings.py
- Fix bare except (E722) in upload_to_sftp.py
- Fix block comment format (E265) in models.py
- Move imports to top of file to fix E402 in celery_app.py, celery_worker.py
- Fix line-too-long (E501) by wrapping strings in multiple files
- Remove unused variable (F841) in upload_to_nextcloud.py

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

app/api/openai.py

@@ -1,10 +1,10 @@
 """
 OpenAI API endpoints
 """
-from fastapi import APIRouter, Request, HTTPException, status
+
 import logging
-import os
-import requests
+
+from fastapi import APIRouter, Request
 
 from app.auth import require_login
 from app.config import settings
@@ -14,6 +14,7 @@ logger = logging.getLogger(__name__)
 
 router = APIRouter()
 
+
 @router.get("/openai/test")
 @require_login
 async def test_openai_connection(request: Request):
@@ -22,54 +23,45 @@ async def test_openai_connection(request: Request):
     """
     try:
         import openai
-        
+
         logger.info("Testing OpenAI API key validity")
-        
+
         # Check if API key is configured
         if not settings.openai_api_key:
             logger.warning("No OpenAI API key configured")
-            return {
-                "status": "error",
-                "message": "No OpenAI API key is configured"
-            }
-        
+            return {"status": "error", "message": "No OpenAI API key is configured"}
+
         # Configure the client
         client = openai.OpenAI(api_key=settings.openai_api_key)
-        
+
         # Try to make a simple request to validate the key
         try:
             # Use a models list endpoint as a simple validation
             models = client.models.list()
-            
+
             # If we got here, the key is valid
             logger.info("OpenAI API key is valid")
             return {
                 "status": "success",
                 "message": "OpenAI API key is valid",
-                "models_available": len(models.data) if hasattr(models, "data") else "Unknown"
+                "models_available": len(models.data) if hasattr(models, "data") else "Unknown",
             }
         except Exception as e:
             error_msg = str(e)
             logger.error(f"OpenAI API key test failed: {error_msg}")
-            
+
             # Determine if this is an authentication error
             is_auth_error = "auth" in error_msg.lower() or "api key" in error_msg.lower()
-            
+
             return {
                 "status": "error",
                 "message": f"API key validation failed: {error_msg}",
-                "is_auth_error": is_auth_error
+                "is_auth_error": is_auth_error,
             }
-    
+
     except ImportError:
         logger.exception("OpenAI package not installed")
-        return {
-            "status": "error",
-            "message": "OpenAI package not installed"
-        }
+        return {"status": "error", "message": "OpenAI package not installed"}
     except Exception as e:
         logger.exception("Unexpected error testing OpenAI connection")
-        return {
-            "status": "error",
-            "message": f"Unexpected error: {str(e)}"
-        }
+        return {"status": "error", "message": f"Unexpected error: {str(e)}"}