Docker-based MCP server

[termoshtt]

• uv-based MCP server has two disadvantage
  • Need for git clone
  • Runs on the local environment without sandboxing
• docker-based MCP server resolves them
  • Much simple install
  • Run in sandboxed environment
• This PR keeps uv-based one as it is since it will be useful for development.

Tasks

• Dockerfile for MCP server
  • docker-compose.yml as a build setting file
  • Push to GitHub Container registry https://github.com/orgs/Jij-Inc/packages/container/package/jij-mcp-server
  • Build and Push docker image on GitHub Actions
    • This workflow is disabled until this PR is merged since this requires permission changes.
• Add Docker version section in README.md
  • Add vscode auto-install link