v0.57.5

Fixed

• Google Calendar sync: all-day events imported from Google no longer show an extra day. Google Calendar stores exclusive end dates per RFC 5545 (a 2-day event Jan 1–2 has end.date = "2026-01-03"); Oikos was storing this value as-is, making every multi-day event appear one day longer than it actually is.
• Google Calendar sync: recurring events with an end date no longer fail to sync to Google with "Invalid recurrence rule." The outbound mapping was sending the recurrence rule without the required RRULE: prefix, which Google's API rejects. Both the missing prefix and the incorrect (non-exclusive) all-day end date in the outbound payload are now fixed.