Is your feature request related to a problem? Please describe.
The absence of a Dockerfile means each developer must manually manage dependencies, Python versions, and tools, which can lead to inconsistencies and onboarding friction.

Use Case: A developer can build a Docker image from the quickstart’s multi_tool_agent, test it locally in any mode, and confidently deploy to Cloud Run with minimal changes.

Describe the solution you'd like
As the first step, I'd like to add a docker directory and Dockerfile inside this directory. This would define a lightweight and portable container environment for adk-python, based on an official Python image.

Describe alternatives you've considered
(1) No Docker Support: Relying on virtual environments works, but lacks the portability and deployment alignment Docker offers, especially for Cloud Run users.
(2) Separate Dockerfiles for each mode (run, web, api_server). This adds complexity and maintenance overhead, so a single Dockerfile with command overrides is preferred with DEV UI (adk web) as default

Additional context

• Ensures consistent environments for testing/debugging and production
• Aligns with ADK’s “Deploy Anywhere” goal by enabling deployments for container environments
• More reliable and less error-prone compared to manual steps

Overall this would improve the developer experience and make it easier to integrate with CI/CD pipelines, cloud deployments, and reproducible builds. I'm happy to submit a PR with a proposed Dockerfile and related documentation to align with the project's goals.

Let me know your thoughts and suggestions !