fix(ui): DNS apply no longer blanks the page + WiFi/DNS modals cover the whole app

Applying DNS assigned the RPC response's fields into networkData without
guarding the shape; the demo mock answered {success:true} with no
servers array, dnsServers became undefined, and the dnsDisplayLabel
computed crashed the whole page render on .length. Guard the assignment,
teach the mock to round-trip DNS state per session, and Teleport the
WiFi + DNS modals to body so they overlay the full app instead of just
the right panel (position:fixed is containing-block-relative inside the
dashboard).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/views/Server.vue

@@ -630,7 +630,11 @@ async function applyDnsConfig(customServers: string) {
     const params: { provider: DnsProviderValue; servers?: string[] } = { provider }
     if (provider === 'custom') { params.servers = customServers.split(',').map(s => s.trim()).filter(s => s.length > 0) }
     const res = await rpcClient.configureDns(params)
-    networkData.value.dnsProvider = res.provider; networkData.value.dnsServers = res.servers; networkData.value.dnsDoH = res.doh_enabled
+    // Never trust the response shape: an undefined `servers` used to reach the
+    // dnsDisplayLabel computed and crash the whole page render on `.length`.
+    networkData.value.dnsProvider = res?.provider ?? provider
+    networkData.value.dnsServers = Array.isArray(res?.servers) ? res.servers : (params.servers ?? [])
+    networkData.value.dnsDoH = !!res?.doh_enabled
     showDnsModal.value = false
   } catch (e) { dnsError.value = e instanceof Error ? e.message : 'DNS configuration failed.' } finally { dnsApplying.value = false }
 }