Maintenance mode activates after current draw completes

- When admin enables maintenance, it's set to 'pending' state
- Maintenance activates automatically after the current draw completes
- Admin can use immediate=true to force immediate activation
- Frontend shows 'Maintenance Scheduled' banner when pending
- Telegram bot warns users but still allows purchases when pending
- Both mode and pending status tracked in system_settings table

back_end/src/routes/admin.ts

@@ -3,7 +3,9 @@ import {
   listCycles, 
   runDrawManually, 
   retryPayout,
-  listPayouts 
+  listPayouts,
+  getMaintenanceStatus,
+  setMaintenanceMode
 } from '../controllers/admin';
 import { verifyAdmin } from '../middleware/auth';
 
@@ -126,5 +128,78 @@ router.get('/payouts', listPayouts);
  */
 router.post('/payouts/:id/retry', retryPayout);
 
+/**
+ * @swagger
+ * /admin/maintenance:
+ *   get:
+ *     summary: Get maintenance mode status
+ *     tags: [Admin]
+ *     security:
+ *       - adminKey: []
+ *     responses:
+ *       200:
+ *         description: Maintenance status
+ *         content:
+ *           application/json:
+ *             schema:
+ *               type: object
+ *               properties:
+ *                 maintenance_mode:
+ *                   type: boolean
+ *                 message:
+ *                   type: string
+ *       403:
+ *         description: Invalid admin key
+ */
+router.get('/maintenance', getMaintenanceStatus);
+
+/**
+ * @swagger
+ * /admin/maintenance:
+ *   post:
+ *     summary: Enable or disable maintenance mode
+ *     description: When enabling, maintenance is set to "pending" and activates after current draw completes. Use immediate=true to activate immediately.
+ *     tags: [Admin]
+ *     security:
+ *       - adminKey: []
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *             required:
+ *               - enabled
+ *             properties:
+ *               enabled:
+ *                 type: boolean
+ *                 description: Whether to enable maintenance mode
+ *               message:
+ *                 type: string
+ *                 description: Custom maintenance message
+ *               immediate:
+ *                 type: boolean
+ *                 description: If true, activate immediately instead of waiting for draw to complete
+ *     responses:
+ *       200:
+ *         description: Maintenance mode updated
+ *         content:
+ *           application/json:
+ *             schema:
+ *               type: object
+ *               properties:
+ *                 maintenance_mode:
+ *                   type: boolean
+ *                 maintenance_pending:
+ *                   type: boolean
+ *                 message:
+ *                   type: string
+ *       400:
+ *         description: Invalid input
+ *       403:
+ *         description: Invalid admin key
+ */
+router.post('/maintenance', setMaintenanceMode);
+
 export default router;