190 dev camila/implement frontend for notifications

[camila-carrillo]

ℹ️ Issue

Closes #190

📝 Description

Implemented the notification popup feature from the bell icon in the header so that users are able to view time-sensitive grant notifications. It's important so that users can keep track of important deadlines.

Briefly list the changes made to the code:

1. Added new components (GrantNotification.tsx, NotificationPopup.tsx) and styles (notifications.css) to display user notifications.
2. Integrated BellButton.tsx with the Satchel store to manage and display notifications.
3. Extended global store (store.ts, actions.ts, mutators.ts) to include a notifications field and a setNotifications mutator.

✔️ Verification

I ran the app locally, and clicked on the bell icon to ensure a popup would come up with dummy data notifications. Clicked the "X" button in the popup to ensure popup would close. Opened DevTools console to confirm that notifications appear in logs, showing store updates. Resized window and tested different screen sizes to ensure popup would stay visible and scale appropriately.

Provide screenshots of any new components, styling changes, or pages.

Test Changes

If your new feature required some test to be changed or added to fit the new functionality or changes please document these changes here.

🏕️ (Optional) Future Work / Notes

Need to replace dummy data with real API call.