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/consumers.py

@@ -0,0 +1,93 @@
+import json
+from channels.db import database_sync_to_async
+from channels.generic.websocket import AsyncWebsocketConsumer
+from django.utils import timezone
+
+
+@database_sync_to_async
+def _mark_notification_read(notification_id, user):
+    from .models import Notification
+    try:
+        n = Notification.objects.get(pk=notification_id, user=user)
+        if not n.is_read:
+            n.is_read = True
+            n.read_at = timezone.now()
+            n.save(update_fields=["is_read", "read_at"])
+        return n.read_at.isoformat()
+    except Notification.DoesNotExist:
+        return None
+
+
+@database_sync_to_async
+def _mark_all_notifications_read(user):
+    from .models import Notification
+    now = timezone.now()
+    return Notification.objects.filter(user=user, is_read=False).update(is_read=True, read_at=now)
+
+
+@database_sync_to_async
+def _delete_notification(notification_id, user):
+    from .models import Notification
+    try:
+        n = Notification.objects.get(pk=notification_id, user=user)
+        n.delete()
+        return True
+    except Notification.DoesNotExist:
+        return False
+
+
+class NotificationConsumer(AsyncWebsocketConsumer):
+
+    async def connect(self):
+        user = self.scope["user"]
+        if not user.is_authenticated:
+            await self.close(code=4401)
+            return
+        self.group_name = f"notifications_{user.pk}"
+        await self.channel_layer.group_add(self.group_name, self.channel_name)
+        await self.accept()
+
+    async def disconnect(self, close_code):
+        if hasattr(self, "group_name"):
+            await self.channel_layer.group_discard(self.group_name, self.channel_name)
+
+    async def receive(self, text_data):
+        data = json.loads(text_data)
+        msg_type = data.get("type")
+
+        if msg_type == "mark_read":
+            notification_id = data.get("id")
+            read_at = await _mark_notification_read(notification_id, self.scope["user"])
+            if read_at:
+                await self.send(text_data=json.dumps({
+                    "type": "notification.read",
+                    "id": notification_id,
+                    "read_at": read_at,
+                }))
+
+        elif msg_type == "mark_all_read":
+            count = await _mark_all_notifications_read(self.scope["user"])
+            await self.send(text_data=json.dumps({
+                "type": "notification.read_all",
+                "marked": count,
+            }))
+
+        elif msg_type == "delete":
+            notification_id = data.get("id")
+            deleted = await _delete_notification(notification_id, self.scope["user"])
+            if deleted:
+                await self.send(text_data=json.dumps({
+                    "type": "notification.deleted",
+                    "id": notification_id,
+                }))
+
+    async def notification_new(self, event):
+        await self.send(text_data=json.dumps({
+            "type": "notification.new",
+            "id": event["id"],
+            "title": event["title"],
+            "text": event["text"],
+            "notification_type": event["notification_type"],
+            "action_url": event.get("action_url"),
+            "created_at": event["created_at"],
+        }))