Add public Docker deployment

[Hrabovszki1023]

What changed

• make the default Compose file pull the public Docker Hub image
• add a separate development build override and a safe .env.example
• mount the console password as a Compose secret
• run the image as a non-root user and add an HTTP-only healthcheck
• document install, verification, MQTT, update and removal on GitHub
• synchronize the GitHub README to the Docker Hub overview after publication
• align the Version 0.1 deployment contract and add deployment tests

Why

The beta needs a reproducible public installation path that does not require
users to build source locally. The container healthcheck must describe process
health without restarting during a temporary battery, gateway or MQTT outage.

Verification

• 255 passed
• python -m ruff check .
• python -m mypy src tests
• git diff --check
• CI validates both Compose configurations and performs the Linux image build

Docker CLI is not installed on the local Windows workspace, so Compose and the
container build are intentionally verified by Linux CI.