Support goal icons

[tolgalive]

This pull request adds support for goal icons in the CommBank web application.

Changes made:

• Added an icon field to the Goal type.
• Displayed goal icons on goal cards.
• Added an emoji picker to the goal manager.
• Updated the selected icon in Redux.
• Sent the updated goal icon to the backend using the existing PUT request.
• Confirmed that selected icons remain visible after refreshing the page.

Testing:

• Ran npm run build successfully.
• Tested selecting an emoji icon in the goal manager.
• Confirmed that the icon appears on the goal card.
• Confirmed that the icon persists after page refresh when connected to the local backend.