Introduce notifications app and integrate emails

Add a new notifications app (models, serializers, views, admin, tasks, consumers, routing, urls, tests) with Notification.notify for in-app websocket pushes and optional email delivery. Centralize email sending in notifications.tasks.send_email_with_context and re-export it from account.tasks for compatibility. Update account and commerce and advertisement tasks to use Notification.notify/_notify_order and the new email helper; adjust order/notification tasks to consolidate logic. Wire notifications into ASGI routing, settings and URL conf. Misc: handle OSError when importing weasyprint, add tmp/ to .gitignore, add local .claude PowerShell checks, add social.blog skeleton, and remove legacy ews-component test files.

backend/notifications/views.py

@@ -0,0 +1,51 @@
+import logging
+from django.utils import timezone
+from rest_framework.decorators import action
+from rest_framework.permissions import IsAuthenticated
+from rest_framework.response import Response
+from rest_framework.viewsets import GenericViewSet
+from rest_framework.mixins import ListModelMixin, RetrieveModelMixin
+from drf_spectacular.utils import extend_schema
+
+from .models import Notification
+from .serializers import NotificationSerializer
+
+logger = logging.getLogger(__name__)
+
+
+@extend_schema(tags=["notifications"])
+class NotificationViewSet(ListModelMixin, RetrieveModelMixin, GenericViewSet):
+    serializer_class = NotificationSerializer
+    permission_classes = [IsAuthenticated]
+
+    def get_queryset(self):
+        return Notification.objects.filter(user=self.request.user)
+
+    @extend_schema(
+        summary="Unread notification count",
+        responses={200: {"type": "object", "properties": {"unread_count": {"type": "integer"}}}},
+    )
+    @action(detail=False, methods=["get"], url_path="unread-count")
+    def unread_count(self, request):
+        count = self.get_queryset().filter(is_read=False).count()
+        return Response({"unread_count": count})
+
+    @extend_schema(summary="Mark a single notification as read", responses={200: NotificationSerializer})
+    @action(detail=True, methods=["post"], url_path="read")
+    def mark_read(self, request, pk=None):
+        notification = self.get_object()
+        if not notification.is_read:
+            notification.is_read = True
+            notification.read_at = timezone.now()
+            notification.save(update_fields=["is_read", "read_at"])
+        return Response(NotificationSerializer(notification).data)
+
+    @extend_schema(
+        summary="Mark all notifications as read",
+        responses={200: {"type": "object", "properties": {"marked": {"type": "integer"}}}},
+    )
+    @action(detail=False, methods=["post"], url_path="read-all")
+    def mark_all_read(self, request):
+        now = timezone.now()
+        updated = self.get_queryset().filter(is_read=False).update(is_read=True, read_at=now)
+        return Response({"marked": updated})