Add weekly new products email and related features

Introduces a weekly summary email for newly added products, including a new email template and Celery periodic task. Adds 'include_in_week_summary_email' to Product and 'newsletter' to CustomUser. Provides an admin endpoint to manually trigger the weekly email, updates Celery Beat schedule, and adds email templates for verification and password reset.

backend/account/views.py

@@ -405,4 +405,7 @@ class PasswordResetConfirmView(APIView):
             user.set_password(serializer.validated_data['password'])
             user.save()
             return Response({"detail": "Heslo bylo úspěšně změněno."})
-        return Response(serializer.errors, status=400)
+        return Response(serializer.errors, status=400)
+    
+
+