Owns the shared :public :named_table ETS table used by every ExAtlas.Fly.Tokens.AppServer.

The table outlives individual AppServer crashes. Only :rest_for_one on the parent ExAtlas.Fly.Tokens.Supervisor can wipe it — by design, because that path also rebuilds every AppServer under the DynamicSupervisor, so the cache and its writers restart together.

ETS schema

{app_name, token, expires_at_unix_seconds}

:public so multiple AppServers can write concurrently. read_concurrency and write_concurrency are both on — cache reads are the hot path and parallel writes are expected under a cold-start thundering herd.