Add Figma persistence and sync flow for one file source.
- create figma_files, figma_file_versions, and figma_comments tables with supporting migrations
- add FigmaSyncService for full and incremental sync, API fetch, pagination, dedupe, and upserts
- add CLI commands and shell wrappers for full and incremental sync runs
- expose Figma dashboard plus API endpoints for summary, snapshots, comments, and admin sync trigger
- wire route and sidebar entry for dashboard access
- trim legacy file_url and thumbnail_url fields, add version label/description support
