Add project progress tracker

[MaharshPatelX]

Summary

• add a living tracker for all 18 project parts
• record completed work, the next part, dependencies, and completion evidence
• add a focused Part 2 checklist and simple tracker maintenance rules
• link the tracker from the README and project blueprint

Current status

• Parts 0 and 1 are complete
• Part 2 — Dataset Source Audit and Ingestion — is next
• Part 17 remains deferred as optional post-MVP work

Validation

• git diff origin/main...HEAD --check passes
• reviewed the exact three-file patch
• documentation-only change; no runtime tests required