26-Jan-2026 — add unique index on ramblersId and deduplicate group codes ref: #138

build 437 — commit d119164

Add unique sparse index on ramblersId to prevent duplicate walk records at the database level when syncing from Ramblers Walk Manager. Add uniqueCommaDelimitedList utility to deduplicate comma-separated group codes when querying the Ramblers API, ensuring consistent filtering regardless of how group codes are configured.