When a reply is relayed across servers, each copy now includes a URL
button underneath the quoted reply text:
- If the referenced message has a relayed copy in the target channel,
the button links to that local copy (so users stay in their own server).
- Otherwise, it falls back to the original message URL.
Works across all relay modes (webhook, embed, compact) and leverages
the existing msg_map to resolve per-channel message IDs.
Bumps version to 3.4.3.
