Update Dockerfile and compose.yml in the infrastructure workstream to support building a containerized test environment capable of executing pytest and validate.py --self-test without host fallback and with network isolation (network_mode: none, read_only: true).
Out of scope: modifying application source code or external repositories.
Dockerfile to install jsonschema and pytest on python:3.12-alpine base.compose.yml with network_mode: none and read_only: true.Updated Dockerfile and compose.yml. The test container configuration runs the full test suite and contract self-test in an isolated container.