What

• Install the [messaging] extra in the published Docker image alongside [all].
• Keep lazy_deps.py available for remaining optional platform packages and future pin bumps.
• Add a Dockerfile contract test so gateway messaging deps stay preloaded.

Why

The official Docker image should start Telegram/Discord gateway adapters without relying on first-boot lazy installation. This addresses the missing python-telegram-bot failure reported in #24698.

Fixes #24698.

How to test

• uv run --with pytest --with pytest-xdist python -m pytest tests/tools/test_dockerfile_pid1_reaping.py tests/test_project_metadata.py -q
• uv run --with pytest --with pytest-xdist python -m pytest tests/tools/test_dockerfile_node_modules_perms.py -q
• uv lock --check
• uv run python scripts/check-windows-footguns.py --all
• git diff --check

Platforms tested

• macOS local checkout for tests above.
• Full Docker image build not run locally.