Add bookmark/favorite support for projects and chapters

## Is your feature request related to a problem? Please describe.
Currently, OWASP Nest does not provide a way for users to save or mark projects or chapters they are interested in.
This makes it difficult for users to quickly return to relevant content, especially as the number of projects and chapters grows. Users must repeatedly search or navigate through the platform to find the same items again.

## Describe the solution you'd like
Introduce a **Bookmark / Favorite** feature that allows users to save projects and chapters for easy access later.

Key functionality:
- A star (favorite) button on project and chapter pages
- Bookmarks persisted per authenticated user
- A dedicated “My Bookmarks” view where users can see all saved items

This would enable a more personalized experience and improve long-term engagement with the platform.

## Describe alternatives you've considered
- **Recently viewed items**: Helps with short-term navigation but does not allow intentional saving.
- **Browser bookmarks**: External to the platform and not user-friendly for managing Nest-specific content.
- **Saved searches**: Useful for discovery, but does not address saving individual projects or chapters.

Bookmarking provides a clearer and more intentional user signal than these alternatives.

## Are you going to work on implementing this?

- [x] Yes
- [ ] No

## Additional context
This feature follows a familiar and well-understood UX pattern (e.g., GitHub Stars, Hoppscotch Collections).
It can also act as a foundation for future enhancements such as personalized dashboards or notifications, while remaining fully useful as a standalone feature.