feat: implement auto-save for forms with draft/publish mode for packs

Commit notes

- Add draftData and draftUpdatedAt columns to samplePacks schema - Add backend API endpoints for draft save, publish, and discard - Create useAutoSave hook for debounced auto-save functionality - Update PackEditDrawer with auto-save to draft and 'Publish Changes' button - Update SampleEditDrawer with direct auto-save on field changes - Add visual indicators for save status (saving, saved, pending, error) - Add discard draft button to revert to published values

Co-authored-by: armin.naimi <[email redacted]>