12-Oct-2026 — remove stale cache entries only after a complete successful sync ref #302

build 999 — commit bbda060

Walks taken off Walks Manager disappear from the group programme after a sync that completed successfully.
If Walks Manager returns an error, an incomplete page, or a malformed list, the existing programme is left as it is instead of being treated as empty.
Only the group, dates and event types that actually synced are considered for removal, so a partial failure cannot wipe other walks.