Set bridge.public_address so relayed messages carry the sender's avatar
(served through a new NPM location for /mautrix-discord/avatar/), listen
on 0.0.0.0 so NPM can reach it, and backfill all Discord messages missed
while the bridge was down.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5