Fix /settings redirect issue and add OAuth admin support

- Convert require_admin_access to proper decorator pattern
- Fix redirect loop that was sending all users to /
- Add is_admin flag handling for OAuth users (checks groups)
- Update SETTING_METADATA with all 102 settings from config.py
- Improve API admin check with type hints

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

app/api/settings.py

@@ -24,9 +24,13 @@ logger = logging.getLogger(__name__)
 router = APIRouter(prefix="/settings", tags=["settings"])
 
 
-def require_admin(request: Request):
+def require_admin(request: Request) -> dict:
     """
     Dependency to ensure the user is an admin.
+    Raises HTTPException if not admin.
+    
+    Returns:
+        User dict from session
     """
     user = request.session.get("user")
     if not user or not user.get("is_admin"):