Fixbug/unknown subjects

[j-nagar]

• Added support in the backend State class to track unknown subjects when inflating saved data.
• Updated the frontend Banner component to display a warning whenever unknown subjects are detected.
• This ensures users are notified if their schedule contains subjects that the system does not recognize.
• Tested by inflating a save containing an unknown subject and verifying that the warning appears in the UI.
• Both manual testing in the browser and console checks were performed to confirm the state updates correctly.