feat: Add manual event notification endpoint for admins

- POST /api/events/:eventId/notify - send notifications from admin's email
- sendSingleEventNotification() uses admin's primary email account
- getSenderAccountByUserId() to get admin's email credentials

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/controllers/event.controller.js

@@ -1,4 +1,5 @@
 import * as eventService from '../services/event.service.js';
+import { triggerSingleEventNotification } from '../cron/index.js';
 
 /**
  * Get calendar data (events + todos) by month
@@ -106,3 +107,24 @@ export const deleteEvent = async (req, res, next) => {
     next(error);
   }
 };
+
+/**
+ * Send notification for an event to all assigned users (admin only)
+ * POST /api/events/:eventId/notify
+ */
+export const sendEventNotification = async (req, res, next) => {
+  try {
+    const { eventId } = req.params;
+    const adminUserId = req.userId;
+
+    const stats = await triggerSingleEventNotification(eventId, adminUserId);
+
+    res.status(200).json({
+      success: true,
+      data: stats,
+      message: `Notifikácie pre "${stats.eventTitle}" odoslané: ${stats.sent}, neúspešné: ${stats.failed}, preskočené: ${stats.skipped}`,
+    });
+  } catch (error) {
+    next(error);
+  }
+};