dashboard: show LAN status in Local Services panel header

- Add lan_enabled to ServerCtx
- Add lan field to /stats API (enabled, peer count)
- Dashboard shows "LAN off" (dim) or "LAN on · N peers" (green)
- Tooltip shows enable command or mDNS service type

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ctx.rs

@@ -39,6 +39,7 @@ pub struct ServerCtx {
     pub timeout: Duration,
     pub proxy_tld: String,
     pub proxy_tld_suffix: String, // pre-computed ".{tld}" to avoid per-query allocation
+    pub lan_enabled: bool,
 }
 
 pub async fn handle_query(