feat: add Docker container support for Claude Agent SDK example app

[74th]

Overview

This PR adds Docker container support for the Claude Agent SDK example application and includes documentation improvements.

Changes

Claude Agent SDK App

• Rename claude_agent_sdk.py to app.py for clarity
• Refactor and improve the Claude Agent SDK example application code structure
• Add Dockerfile and docker-compose.yml for containerized deployment
• Add .dockerignore to optimize Docker build context
• Add pyproject.toml and uv.lock for explicit dependency management within the container

VOICEVOX

• Add docker-compose.yml under misc/voicevox/ for running VOICEVOX in a container

Documentation

• Add docs/create_docker_container_ja.md: Guide for building and running the Claude Agent SDK app in a Docker container
• Add docs/create_your_claude_agent_sdk_apps.md: Guide for creating custom Claude Agent SDK apps
• Update docs/setup_ja.md, docs/run_sample_app_ja.md, docs/server_ja.md, and README.md to reflect the new Docker-based workflow

Example Apps

• Update echo_with_move.py and gemini.py with improvements
• Remove unused code from echo.py
• Remove .python-version file (replaced by container-based environment management)