feat(NetworkMapScheduler): add next scheduled run time to settings response and update frontend to display next run time

backend/routes/schedulerRoutes.js

@@ -32,7 +32,8 @@ async function getNetworkMapSchedulerSettings(req, res) {
   try {
     const ui = await readUiSettings();
     const settings = networkMapScheduler.getSettingsFromUiSettings(ui);
-    return res.json(settings);
+    const nextRunAt = networkMapScheduler.getNextRunAt(settings);
+    return res.json({ ...settings, nextRunAt: nextRunAt || undefined });
   } catch (e) {
     console.error('[scheduler] getSettings', e);
     return sendError(res, 500, 'Не удалось прочитать настройки', 'E_SCHEDULER');