feat: Implement paginated project listing

[masch]

This PR implements the functionality to list registered projects on-chain with pagination support, mirroring the existing DAO pagination pattern but optimized for storage efficiency. This functionality follows the requirements for #331.

Key Changes

• Contract Interface:

  • Added get_projects(page: u32) to the VersioningTrait to retrieve projects page by page.

• Storage Optimization:

  • Introduced ProjectKey::ProjectKeys(u32) to store a list of project keys for each page.
  • Refactored the storage approach to save only Vec<Bytes> (keys) per page rather than duplicating project data.
  • get_projects now retrieves the keys for the requested page and fetches the full Project details for each key on demand.

• Error Handling:

  • Added ContractErrors::NoProjectPageFound to handle out-of-bounds page requests gracefully.

• Tests:

  • Added tests/test_project_list.rs covering:
    • Pagination logic (verifying correct items per page).
    • Data correctness for retrieved projects.
    • Error handling for invalid page requests.

This implementation ensures efficient storage usage while providing a robust way to traverse all registered projects.

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[tupui]

Thanks for working on this @masch It's a good start, I left some comments.

[masch]

@tupui Great tips! Let me know what do you think.

[tupui]

ok I think we are really close 😃

[tupui]

Thanks again. I will merge once the CI is green. Looking forward to the follow up 😃