A missing avatar was a 404, which the browser reports as an error for every
such sender on every page. It is now an empty 204: the <img> still fails to
decode it and the initials show through, but nothing is logged, and the miss
carries the same one-day browser cache as a hit so it stops being re-fetched.
On a phone the mail list's rows sit 20px apart instead of 7px.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The shared Redis client decodes replies as UTF-8 text, but the avatar cache
holds raw image bytes and a b"none" miss marker: an image could not be read
back at all, and a miss came back as str and crashed on .partition(b"\n").
Only a sender's first request worked; after that, a 500. The cache now goes
through a binary-safe client, get_redis_bytes().
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>