Add notification history feature with bell icon and history page

- Add notification_history database table for logging all triggered notifications
- Create API endpoints for fetching recent and historical notifications
- Add NotificationBell component in navbar with badge showing recent count
- Dropdown shows 5 most recent notifications with links to products
- Create full NotificationHistory page with filtering by notification type
- Log notifications when sent: price drops, target prices, back-in-stock
- Track which channels (telegram, discord, pushover, ntfy) received each notification
- Update sendNotifications to return which channels succeeded
- Bump version to 1.0.3

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

backend/src/routes/notifications.ts

@@ -0,0 +1,72 @@
+import { Router, Response } from 'express';
+import { authMiddleware, AuthRequest } from '../middleware/auth';
+import { notificationHistoryQueries } from '../models';
+
+const router = Router();
+
+// All routes require authentication
+router.use(authMiddleware);
+
+// Get recent notifications (for bell dropdown)
+router.get('/recent', async (req: AuthRequest, res: Response) => {
+  try {
+    const userId = req.userId!;
+    const limit = Math.min(parseInt(req.query.limit as string) || 10, 20);
+
+    const notifications = await notificationHistoryQueries.getRecent(userId, limit);
+    const recentCount = await notificationHistoryQueries.countRecent(userId, 24);
+
+    res.json({
+      notifications,
+      recentCount,
+    });
+  } catch (error) {
+    console.error('Error fetching recent notifications:', error);
+    res.status(500).json({ error: 'Failed to fetch notifications' });
+  }
+});
+
+// Get notification history with pagination
+router.get('/history', async (req: AuthRequest, res: Response) => {
+  try {
+    const userId = req.userId!;
+    const page = parseInt(req.query.page as string) || 1;
+    const limit = Math.min(parseInt(req.query.limit as string) || 20, 100);
+    const offset = (page - 1) * limit;
+
+    const [notifications, totalCount] = await Promise.all([
+      notificationHistoryQueries.getByUserId(userId, limit, offset),
+      notificationHistoryQueries.getTotalCount(userId),
+    ]);
+
+    res.json({
+      notifications,
+      pagination: {
+        page,
+        limit,
+        totalCount,
+        totalPages: Math.ceil(totalCount / limit),
+      },
+    });
+  } catch (error) {
+    console.error('Error fetching notification history:', error);
+    res.status(500).json({ error: 'Failed to fetch notification history' });
+  }
+});
+
+// Get count of recent notifications (for badge)
+router.get('/count', async (req: AuthRequest, res: Response) => {
+  try {
+    const userId = req.userId!;
+    const hours = parseInt(req.query.hours as string) || 24;
+
+    const count = await notificationHistoryQueries.countRecent(userId, hours);
+
+    res.json({ count });
+  } catch (error) {
+    console.error('Error counting notifications:', error);
+    res.status(500).json({ error: 'Failed to count notifications' });
+  }
+});
+
+export default router;