Add Dockerfile and update devcontainer configuration for Python envir…

[SteveCInVA]

This pull request updates the development container and deployment scripts to improve Python environment management and dependency installation. The main changes include switching to a custom Dockerfile for the dev container, ensuring dependencies are installed in a virtual environment, and updating post-deployment commands to consistently use the virtual environment's Python interpreter.

Development environment improvements:

• Switched the dev container setup from using a prebuilt Python image to building from a custom Dockerfile (.devcontainer/Dockerfile), which now installs the xz-utils package. [1] [2]
• Updated the devcontainer configuration to build with a specific Python version, and set up the Python virtual environment (.venv) for dependency management. The postCreateCommand now creates a virtual environment and installs requirements into it, and VS Code is configured to use the virtual environment's Python interpreter by default (.devcontainer/devcontainer.json). [1] [2] [3]

Deployment script improvements:

• Modified the Azure deployment hook to install Python dependencies into a virtual environment instead of user space, and ensured post-deployment scripts are run using the virtual environment's Python interpreter (deployers/azure.yaml). [1] [2]

Documentation:

• Added a step to the Bicep deployment README instructing users to run az login before authenticating with azd (deployers/bicep/README.md)

[Copilot]

Pull request overview

This PR updates the devcontainer and Azure deployment hooks to use a repo-local virtual environment (.venv) for Python dependency installation, and adds a small docs improvement for Bicep-based deployment setup.

Changes:

• Switch devcontainer from a prebuilt Python image to a custom Dockerfile, and create/install dependencies into .venv.
• Update deployers/azure.yaml to create a .venv and run postconfig using the venv interpreter.
• Add an az login step to the Bicep deployment README.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
deployers/bicep/README.md	Adds an az login step before azd auth login (contains a small typo).
deployers/azure.yaml	Creates a Python venv for deployment-time scripting and runs postconfig.py from it.
.devcontainer/devcontainer.json	Switches devcontainer to build from local Dockerfile and installs dependencies into .venv.
.devcontainer/Dockerfile	New Dockerfile that installs xz-utils on top of a base Ubuntu devcontainers image.

Comments suppressed due to low confidence (1)

.devcontainer/devcontainer.json:19

• The base image in the custom devcontainer Dockerfile is devcontainers/base:ubuntu, so you rely entirely on the python feature for installing Python. If you need a specific Python version (3.11 per VARIANT), pin it in the feature config; otherwise developers may end up with a different default Python version than intended.

	"features": {
		"ghcr.io/devcontainers/features/docker-in-docker:2": {
			"version": "latest"
		},
		"ghcr.io/devcontainers/features/python:1": {},
		"ghcr.io/devcontainers-extra/features/black:2": {},

[Copilot]

Typo in the az login description: "shta" should be "that" (and the sentence could be tightened for clarity).

Suggested change

	`az login` - this will open a browser window shta the user with Owner level permissions to the target subscription will need to authenticate with.
	`az login` - opens a browser window where a user with Owner level permissions to the target subscription must authenticate.

[Copilot]

VARIANT build arg is set here but the .devcontainer/Dockerfile never declares/uses ARG VARIANT, so this currently has no effect (and doesn't actually pin the Python version). Either use a Python base image keyed off VARIANT, or remove this arg and configure the Python feature version explicitly.

[Copilot]

Consider cleaning up apt metadata to keep the devcontainer image smaller and more reproducible (e.g., --no-install-recommends and removing /var/lib/apt/lists/* after install).

Suggested change

	RUN apt-get update && apt-get install -y xz-utils
	RUN apt-get update \
	&& apt-get install -y --no-install-recommends xz-utils \
	&& rm -rf /var/lib/apt/lists/*

[Copilot]

For consistency/portability, prefer invoking the venv interpreter as .venv/bin/python (not python3). Some venvs only guarantee python exists, and your devcontainer config also points VS Code at .venv/bin/python.

Suggested change

	if .venv/bin/python3 ./bicep/postconfig.py; then
	if .venv/bin/python ./bicep/postconfig.py; then

[Copilot]

This redirects all output (including venv creation failures) to /dev/null, which will make deployment failures harder to diagnose now that python3 -m venv is part of the command chain. Consider only silencing successful pip install output and printing captured stderr/stdout on failure.

Suggested change

	if python3 -m venv .venv && .venv/bin/pip install -r ./bicep/requirements.txt > /dev/null 2>&1; then
	echo "✓ Dependencies installed successfully"
	else
	echo "✗ ERROR: Failed to install Python dependencies" >&2
	if python3 -m venv .venv; then
	if pip_output=$(.venv/bin/pip install -r ./bicep/requirements.txt 2>&1); then
	echo "✓ Dependencies installed successfully"
	else
	echo "$pip_output" >&2
	echo "✗ ERROR: Failed to install Python dependencies" >&2
	exit 1
	fi
	else
	echo "✗ ERROR: Failed to create Python virtual environment" >&2