Add optional color column to spool list showing filament color swatches
with multi-select filtering capability.
Backend:
- GET /api/v1/color endpoint to list distinct filament colors
- filament.color_hex query param on spool list for filtering
Frontend:
- ColorFilterColumn component renders color swatches
- useSpoolmanColors() hook fetches available colors
- Filter dropdown shows swatches with hex codes
- Column hidden by default (enable via column selector)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
