Update documentation links for d2lang

[alixander]

What changed

• Update active D2, Docs, Playground, VS Code, Vim, and Obsidian repository links to the d2lang organization.
• Update the d2-vscode submodule URL while retaining the shared terrastruct/ci submodule.
• Update current installation, editor, community, release, blog, and Korean documentation references.

Validation

• Docusaurus production build completed successfully for English and Korean.
• git diff --check passed.
• Remaining old repository links are confined to historical release content or unchanged submodules.