v1.4.1 — Filtered search fix

Filtered searches no longer come up short — a recall into a large namespace could return fewer memories than exist, and now keeps scanning until it has enough.

This is insurance rather than a repair: nothing is known to be affected today, and the database is empty. It turns on pgvector's iterative scan for every connection, and logs one warning if the database's pgvector is older than 0.8.

Full changelog: v1.4.0...v1.4.1