feat(diagnostics): UI-Tools — ping/traceroute/dig/curl/tcp

Operator-Diagnose ohne SSH. Sidebar → System → Diagnose.

internal/services/diagnostics/:
  - Ping        — ping -c4 -W2 (12s timeout)
  - Traceroute  — traceroute -n -w2 -q1 -m20 (60s timeout)
  - Dig         — dig +timeout=3 +tries=2 <TYPE> <NAME> (Types A/AAAA/
                  CNAME/MX/TXT/NS/SOA/PTR/SRV/CAA whitelisted)
  - Curl        — curl -IsSv --max-time 10 (nur http(s)://, kein
                  file:// / smb:// / data://)
  - TCPProbe    — nc -zv -w5 (8s timeout)

Sicherheit: validTarget() prüft jeden Input gegen Allow-List
[a-zA-Z0-9.:/_-]; verhindert Shell-Metachar-Injection. exec.Command
mit nackten Argument-Slices (kein /bin/sh, kein Glob-Expansion).

internal/handlers/diagnostics.go: POST /api/v1/diagnostics/<tool>
hinter requireAuth.

UI (pages/Diagnostics): 5 Tool-Cards, jede mit eigenem Input + Run-
Button + monospace-Output-Pane (dunkel, scrollbar, max-height 320px).
Pro Tool ein Status-Tag (OK / exit N) + Dauer-ms. info-Alert oben
erklärt dass Tools auf der Box laufen, nicht im Browser; security-
Alert unten erklärt die Restrictions.

control: iputils-ping, traceroute, dnsutils, curl, netcat-openbsd
als Depends. Auf Test-Box bereits da (waren Distro-defaults).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

management-ui/src/App.tsx

@@ -28,6 +28,7 @@ const ClusterPage = lazy(() => import('./pages/Cluster'))
 const FirewallLivePage = lazy(() => import('./pages/FirewallLive'))
 const LogsPage = lazy(() => import('./pages/Logs'))
 const BackupsPage = lazy(() => import('./pages/Backups'))
+const DiagnosticsPage = lazy(() => import('./pages/Diagnostics'))
 const LicensePage = lazy(() => import('./pages/License'))
 const SettingsPage = lazy(() => import('./pages/Settings'))
 
@@ -115,6 +116,7 @@ export default function App() {
                   <Route path="/cluster" element={<ClusterPage />} />
                   <Route path="/logs" element={<LogsPage />} />
                   <Route path="/backups" element={<BackupsPage />} />
+                  <Route path="/diagnostics" element={<DiagnosticsPage />} />
                   <Route path="/license" element={<LicensePage />} />
                   <Route path="/settings" element={<SettingsPage />} />
                 </Route>