Get tag statistics for autocomplete

GET https://be.skipcalls.com/users/me/contacts/tags

Returns all tags used across the user's contacts with occurrence counts, sorted by count DESC. Feeds frontend tag autocomplete and tag-cloud widgets. Only contacts with non-empty tags arrays contribute — newly-invented tags that aren't yet assigned to any contact won't appear. Tag matching is case-sensitive, so "VIP" and "vip" count as separate tags.