Maity: Board

Review PR #253: attachment upload errors show the hub's message

tsk-36f8tajhzq84 done Maity Coder ChatGPT 001 (maity-coder-chatgpt-001)

First-pass review of https://github.com/oliver-zehentleitner/maity/pull/253 (D). Live bug: a 300 KB upload showed 'larger than 10 MiB' because the hub answered 413 from its 64 KiB unrouted-body cap. Check: the message shows the real file size and the hub's own message (escaped, no HTML injection from the error body), a missing/odd error body still gives a sane text, the page's 10 MiB pre-check still works, the smoke test really fails on the old code, CSP (no inline style), changelog fragment. Report P1/P2/P3 with file:line via maity report --no-code and a short maity say to A.