Upload README.md

Update nav: Images: obox / Images: Google Drive

Add Two Variants comparison table and test/validation split docs

Revert test.json to PB version and add validation set

Sync nav icons and align leaderboard description with paper abstract.

Update link labels in Dataset Card

Add quick links section to Dataset Card

Change task_categories to text-to-image

Fix task_categories to use official HF value

Rename PhotoBench-Full to PhotoBench in Dataset Card

Restructure as HF Dataset repository

Initial PhotoBench-Full download page