Prevent email bombing attacks on the send-user-feedback endpoint by
limiting the error-report field to 1MiB and adding climit rate limits:
by-profile (1 permit, queue 3) and global (4 permits), configured in
climit.edn. Make the schema public so it can be exercised by tests,
and add schema validation tests covering the new size limit.
AI-assisted-by: qwen3.7-plus
