Varaverk: rsync flag toggle + stop button

- Rsync/rsync.sh children in Advanced now show as conf_flag type when the
  parent orch controls a *_RSYNC_ENABLED tier flag; toggle writes true/false
  to master.conf instead of comment/uncommenting a SCRIPTS array entry
- Added vv_conf_flag_value() and vv_conf_flag_set() helpers in scheduler.php
- Added api/flag_toggle.php endpoint (validates *_RSYNC_ENABLED pattern)
- Added api/stop.php: kills process group, sweeps stuck locks, updates stat
- vv-flag-badge CSS (amber, monospace) to distinguish from event/script rows
- vvSaveChild() routes conf_flag children to flag_toggle.php unconditionally
- vvApplyOrchState() keeps conf_flag toggle at real flag value; disables when orch off
- vvSaveAll() skips conf_flag children (immediate-save only)

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

@@ -0,0 +1,14 @@
+<?php
+header('Content-Type: application/json');
+require_once dirname(__DIR__) . '/include/scheduler.php';
+
+$name    = trim($_POST['name']    ?? '');
+$enabled = ($_POST['enabled'] ?? '0') === '1';
+
+if (!$name || !preg_match('/^[A-Z_]+_RSYNC_ENABLED$/', $name)) {
+    echo json_encode(['ok' => false, 'error' => 'Invalid flag name']);
+    exit;
+}
+
+$ok = vv_conf_flag_set($name, $enabled);
+echo json_encode(['ok' => $ok, 'error' => $ok ? null : 'Failed to write master.conf']);