Upgrade vulnerable Python dependencies

Raise the supported Python floor to 3.11 for patched dependency releases and update CI/runtime metadata.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

README.md

@@ -1,6 +1,6 @@
 # Getting started
 
-Before starting, make sure you have Python 3.9 and Node.js 20 available.
+Before starting, make sure you have Python 3.11 or newer and Node.js 20 available.
 
 ```bash
 uv run manage.py migrate