Implement Favorite Proposal Toggle & Persistence

[minikin]

Summary

Allow users to mark/unmark proposals as favorites, storing the state locally for persistence.

Description

• Add a favorite (⭐️) button to the proposal details header.
• Implement toggle functionality:
  • Clicking the button adds/removes the proposal from Favorites.
  • The button updates visually to reflect the favorited state.
• Store Favorites list locally:
  • Use local database .
  • Link saved favorites to the Proposal ID.
• Ensure Favorites persist after page refresh.
• Use mock data for now; replace with API integration later.

Acceptance Criteria

• Users can mark/unmark a proposal as Favorite by clicking the ⭐️ button.
• The button updates visually when toggled.
• Favorites are stored locally and persist after reload.
• Works entirely on the frontend (backend does not track favorites).
• UI follows the Figma design and updates smoothly.

References

Depends on

• Implement persistence storage #1454
• Implement Proposal Details Page #1622