Warning summary boxes in the import wizard had white text on a
light warning background, making them unreadable. Switch to a
light-yellow background with dark text instead.
Also adds convert_xlsx.py for converting the LvS member Excel
spreadsheet into CSV files for ZIP bundle import, and documents
the mandatory version bump rule in CLAUDE.md.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
shahondin1624