Add goal icon support

[SIDDHARTH-18-MARU]

Summary

Implemented goal icon support across the CommBank application.

Changes Made

• Added icon field to the Goal model.
• Displayed icons on Goal Cards.
• Implemented emoji picker for selecting icons.
• Updated Goal Manager to add and edit icons.
• Added PUT request to persist icon changes.
• Updated emoji selection handler to save icon changes to the backend.
• Added unit tests for the GetGoalsForUser endpoint.

Testing

• Verified emoji selection and icon updates.
• Verified icon persistence after refresh.
• All backend tests pass successfully.