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/views/base.py

@@ -1,15 +1,17 @@
 """
 Base setup for views, containing shared functionality and imports.
 """
-from fastapi import APIRouter, Request, Depends, HTTPException
-from fastapi.templating import Jinja2Templates
-from pathlib import Path
-from sqlalchemy.orm import Session
-import logging
 
-from app.auth import require_login
-from app.database import SessionLocal
+import logging
+from pathlib import Path
+
+from fastapi import APIRouter, Depends, HTTPException, Request  # noqa: F401
+from fastapi.templating import Jinja2Templates
+from sqlalchemy.orm import Session  # noqa: F401
+
+from app.auth import require_login  # noqa: F401
 from app.config import settings
+from app.database import SessionLocal
 
 # Set up Jinja2 templates
 templates_dir = Path(__file__).parent.parent.parent / "frontend" / "templates"
@@ -22,6 +24,7 @@ templates.env.globals["max"] = max
 # Customize Jinja2Templates to include app_version in all templates
 original_template_response = templates.TemplateResponse
 
+
 def template_response_with_version(*args, **kwargs):
     """Wrapper for TemplateResponse to include version in all templates"""
     # If context dict is provided, add version to it
@@ -31,11 +34,13 @@ def template_response_with_version(*args, **kwargs):
         kwargs["context"].setdefault("version", settings.version)
     return original_template_response(*args, **kwargs)
 
+
 templates.TemplateResponse = template_response_with_version
 
 # Set up logging
 logger = logging.getLogger(__name__)
 
+
 def get_db():
     """
     Dependency to get a database session.