feat: prevent duplicate project registrations with metadata validatio…

[mayasimi]

resolve #5

Summary

This PR implements logic to prevent duplicate project registrations in the Project Registry.

What Was Added

• Validation to reject duplicate project submissions.
• Duplicate detection based on project metadata (including name, description, category, and owner).
• Clear error handling with explicit failure message.
• Unit tests covering:
  • Exact duplicate submission (expected to fail)
  • Different projects with unique metadata (expected to succeed)

Expected Behavior

• Contract rejects duplicate submissions.
• Slightly different projects are allowed.
• On-chain data integrity is preserved.

Test Results

All unit tests pass successfully:
17 passed; 0 failed.

Impact

Prevents registry clutter and ensures data integrity on-chain.