Add web UI reboot/shutdown controls and system action API

templates/index.html

@@ -36,6 +36,15 @@
       <h2>Serial Monitor</h2>
       <a href="/serial">Zur Live-Serial-Seite</a>
     </section>
+
+    <section class="card">
+      <h2>System</h2>
+      <div class="button-row">
+        <button id="rebootBtn" class="btn-secondary">Reboot</button>
+        <button id="shutdownBtn" class="btn-danger">Shutdown</button>
+      </div>
+      <div id="systemMsg"></div>
+    </section>
   </main>
 
   <script>
@@ -86,7 +95,7 @@
       const msg = document.getElementById('connectMsg');
 
       if (!ssid) {
-        msg.textContent = 'Bitte SSID wählen.';
+        msg.textContent = 'Bitte SSID waehlen.';
         return;
       }
 
@@ -109,8 +118,32 @@
       setTimeout(refreshStatus, 1000);
     }
 
+    async function triggerSystemAction(action) {
+      const msg = document.getElementById('systemMsg');
+      const label = action === 'reboot' ? 'Reboot' : 'Shutdown';
+      const ok = window.confirm(`System wirklich ${label.toLowerCase()} ausfuehren?`);
+      if (!ok) {
+        return;
+      }
+
+      msg.textContent = `${label} wird gestartet...`;
+      try {
+        const resp = await fetch(`/api/system/${action}`, {method: 'POST'});
+        const data = await resp.json();
+        if (resp.ok && data.ok) {
+          msg.textContent = `${label} ausgeloest.`;
+        } else {
+          msg.textContent = `Fehler: ${data.message || 'Aktion fehlgeschlagen'}`;
+        }
+      } catch (e) {
+        msg.textContent = `${label} fehlgeschlagen.`;
+      }
+    }
+
     document.getElementById('scanBtn').addEventListener('click', scan);
     document.getElementById('connectBtn').addEventListener('click', connectWifi);
+    document.getElementById('rebootBtn').addEventListener('click', () => triggerSystemAction('reboot'));
+    document.getElementById('shutdownBtn').addEventListener('click', () => triggerSystemAction('shutdown'));
 
     refreshStatus();
     setInterval(refreshStatus, 5000);