Update Docker base image to Python 3.11.15

[PeterDaveHello]

GitHub Copilot Pull Request Summary:

This pull request updates the Python base image version used in the Dockerfile for both the build and application stages. The main change is upgrading from Python 3.11.11 to 3.11.15, which brings in the latest bug fixes and security patches.

Dependency and environment updates:

• Updated the base image in the Dockerfile from python:3.11.11-slim-bookworm to python:3.11.15-slim-bookworm for both the builder and app stages.