use anyio and fixup process handling

[swelborn]

---

This is part 5 of 10 in a stack made with GitButler:

•  10  remove jwt/jwks from this #14
•  9  add idle timeout option #13
•  8  refactor into functional core/imperative shell #12
•  7  add alembic for migrations #11
•  6  use a key to dedupe reqs #10
•  5  use anyio and fixup process handling #9 👈
•  4  systemd + vault certs #8
•  3  feat: caller dictates the cache log path; drop RUN_DIR #7
•  2  minor model updates and configuration change since timeout was added #6
•  1  create ports locally to fastcache server #5