Replaces the single workforce_rota config snapshot (which was overwritten
on each sync, losing data when switching weeks) with a workforce_daily_shifts
table keyed by date. Sync now covers a rolling today-7 to today+28 window
unconditionally — no date params needed. Each date's record carries a
synced_at timestamp so the UI shows the age of the oldest date in view.
Mid-week viewing works naturally since data is stored per date not per week.
source column reserved for future timesheet replacement of past dates.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
