UUIDv7 generation for Asobi entities.

Generates UUIDv7 (RFC 9562) identifiers via jhn_uuid. UUIDv7 embeds a millisecond timestamp in the high 48 bits, giving time-ordered IDs that improve PostgreSQL B-tree index locality, reduce WAL writes, and enable native time-range queries on primary keys.

Privacy note (F-31): the embedded timestamp leaks the creation time of any id we expose. Match ids, world ids, ticket ids and similar ephemeral resources are an accepted trade-off, but player.id — which uses the same generator and persists for life — also reveals account-creation time. Treat the trade-off as acceptable for this codebase; if a future requirement needs unguessable, non-correlatable ids (e.g. for tokens, invite codes, etc.) generate them via crypto:strong_rand_bytes/1 rather than this function.