feat: pwa notifications

tracker/views.py

@@ -1,6 +1,7 @@
 from datetime import timedelta
 from typing import Optional
 
+from django.conf import settings
 from django.contrib import messages
 from django.contrib.admin.views.decorators import staff_member_required
 from django.shortcuts import redirect, render
@@ -103,5 +104,7 @@ def today(request):
             "next_date": day + timedelta(days=1),
             "chart": build_chart(readings),
             "reading_count": len(readings),
+            # Empty when push is not configured; the page then hides the card.
+            "vapid_public_key": settings.VAPID_PUBLIC_KEY,
         },
     )