Document libp2p 2.2.8 peer domain behavior

[abn2357]

Summary

• document domain-name support for seed, active, passive, fast-forward, and backup peer configuration
• clarify address formats, DNS resolution failures, and backup-only periodic refresh behavior
• correct the DNS tree configuration path to node.dns.treeUrls
• update the master-slave deployment guide for domain and IPv6 backup members

Why

libp2p 2.2.8 and the corresponding java-tron integration add peer-domain resolution and stricter IPv6 validation. The operational documentation needs to distinguish normal peer lists from node.backup.members and from DNS tree discovery.

User impact

Operators can configure supported peer domains with the correct address format and understand which failures are skipped, which abort startup, and which domains refresh automatically.

Validation

• git diff --check
• mkdocs build passed
• verified behavior against java-tron and libp2p 2.2.8 source