pgx v5 cannot scan a PostgreSQL DATE column directly into a Go string.
The WHERE clause already used week_start::text but the SELECT did not,
causing GetByWeek to return a scan error that the GenerateMenu handler
swallowed without logging (just returned 500).
- repository.go: SELECT mp.week_start::text instead of mp.week_start
- handler.go: add slog.Error before the silent 500 branch
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>