Update python packages

Author: leekahung

backend/pyproject.toml

@@ -5,6 +5,10 @@ version = "0.2.0"
 requires-python = ">=3.12"
 dependencies = [
   "flask>=3.1.1",
+  "flask-mailman",
+  "Flask_Limiter",
+  "xhtml2pdf",
+  "redis",
   "valkey>=6.1.0",
   "gunicorn>=23.0.0",
   "google-auth>=2.40.3",