varaverk: System card (identity/time/uptime/buttons); merge Fallback+Partner into one card

Plugin/usr/local/emhttp/plugins/varaverk/api/system.php

@@ -0,0 +1,20 @@
+<?php
+header('Content-Type: application/json');
+
+$body  = json_decode(file_get_contents('php://input'), true) ?? [];
+$action = $body['action'] ?? '';
+
+$allowed = ['stop', 'shutdown', 'restart'];
+if (!in_array($action, $allowed, true)) {
+    echo json_encode(['ok' => false, 'error' => 'invalid action']);
+    exit;
+}
+
+$cmd = match($action) {
+    'stop'     => '/usr/local/sbin/mdcmd stop',
+    'shutdown' => '/sbin/shutdown -h now',
+    'restart'  => '/sbin/shutdown -r now',
+};
+
+exec($cmd . ' > /dev/null 2>&1 &');
+echo json_encode(['ok' => true]);