LoadConfig read SPREADSHEET_ID, but the .env defines GOOGLE_SHEETS_ID,
so config loading failed. The default SHEET_RANGE was also a hardcoded
'Dyżury!A1:F100', but the spreadsheet tabs are named per year (e.g.
'2026'), producing a 400 'Unable to parse range'. Read GOOGLE_SHEETS_ID
and derive the default range from the current year.
Add a RUN_LIVE-gated integration test that drives the full
LoadConfig -> Service -> Syncer.Sync -> Store path against the live
Sheet, and gitignore the generated rota.json cache.
Kamil 'Kamaś' Bruchal