PPHA-475: Use python slim over alpine linux

Alpine linux causes some DNS issues in particular NHS Login sandbox.

Pre hardened images may be the way forward, eventually, avoiding musl
libc which causes the DNS issues in kubernetes / Azure container apps

Author: Themitchell

Dockerfile

@@ -8,7 +8,7 @@ RUN npm ci
 RUN npm run compile
 
 
-FROM python:3.14.1-alpine3.21 AS python_base
+FROM python:3.14.2-slim AS python_base
 
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1 \