Add chore expiry notification system with scheduling and tests

- Implemented `trigger_chore_expiry.py` script to manually trigger chore expiry notifications for users via the admin API.
- Developed `chore_expiry_notification_scheduler.py` to handle the logic for sending notifications for chores expiring within the next 75 minutes.
- Created utility functions in `schedule_utils.py` to determine scheduling and deadlines for chores.
- Added comprehensive tests for the chore expiry notification system in `test_chore_expiry_notification_scheduler.py`, covering various scenarios including scheduled chores, confirmations, and user settings.

frontend/vue-app/public/sw.js

@@ -20,14 +20,19 @@ self.addEventListener('push', function (event) {
   }
 
   const title = payload.title || 'Reward App'
+  // Expiry-warning notifications are informational only — no action buttons
+  const actions =
+    payload.type === 'chore_expiring_soon'
+      ? []
+      : [
+          { action: 'approve', title: 'Approve' },
+          { action: 'deny', title: 'Deny' },
+        ]
   const options = {
     body: payload.body || '',
     icon: '/icons/icon-192x192.png',
     data: payload,
-    actions: [
-      { action: 'approve', title: 'Approve' },
-      { action: 'deny', title: 'Deny' },
-    ],
+    actions,
   }
 
   event.waitUntil(self.registration.showNotification(title, options))