Show template definition link in container form

[Copilot]

The new-container form's template dropdown gave no way to inspect what a template actually contains (installed packages, versions). Users had no path from a selected template to its source definition.

Changes

• ContainerFormPage.tsx
  • Added a definition source URL to each entry in COMMON_TEMPLATES, pointing at the image's defining source (Dockerfile directory under images/, or the mieweb/ozwell-studio repo).
  • Render a "View template definition" external link below the Template selector, shown only when a built-in template is selected (hidden for the placeholder and Custom…).

const definition = COMMON_TEMPLATES.find((t) => t.value === template)?.definition;
// ...
<a href={definition} target="_blank" rel="noopener noreferrer" ...>
  <ExternalLink className="size-3 shrink-0" aria-hidden="true" />
  <span>View template definition</span>
</a>

Notes

• NodeJS 24 + Docker (docker-nodejs) links to images/docker, since per images/docker-bake.hcl it reuses the docker Dockerfile with the nodejs base context — no separate images/docker-nodejs directory exists. This matches the existing mapping in docs/developers/docker-images.md.
• The screenshot annotation "Confirm this has Docker in it" refers to Ozwell Studio's image contents, which is outside this repo (mieweb/ozwell-studio) and not changed here.