[FEATURE] In-app diagnostics view for LAN connectivity health

[krwg]

Summary

Read-only surfaced panel exposing selected runtime facts (bound UDP/TCP ports, reachable broadcast flag self-test TTL, firewall hints) — NOT an external port scanner replacing OS tools.

Background

Users misattribute application bugs to Windows Defender rules.

Scope

• Surface last discovery announce timestamp deltas.
• Show active peer sockets count and last TCP error string if any.
• Link to distilled troubleshooting doc excerpt.

Acceptance criteria

• Accessible from Settings → Advanced collapsible requiring explicit expand.
• Sensitive paths redacted (userData shortened).
• Refresh button clears transient probe cache.

Technical notes

Run lightweight self-ping optionally on user click only — never automatic aggressive scanning.

Definition of done

Simulate blocked UDP log line surfaces human actionable string.