- Create vendor_daily_data table schema and Supabase client service
- Add upload API route for Vendor Central CSV parsing and upsert
- Add VendorDataView with BSR trend, ratings, and buy box charts
- Integrate new Vendor tab into app navigation (desktop + mobile)
- Add vendor CSV upload card to FileUpload modal
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>