Add artifact registry organization settings activation scaffold

What does this MR do and why?

Add the EE organization Artifact Registry settings page for monolith/S01 (Step 5a): the Apollo-wired Vue bootstrap and the page entrypoint that mounts it into the settings page stood up in Step 5.

The page ships a single Activation section scaffold - a framework-shared SettingsBlock carrying the section's title and description and no body - which monolith/S10 fills with the activation controls.

Section copy is taken from the settings design proposal.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the feature flag in the Rails console:

   Feature.enable(:ui_for_organizations)
   Feature.enable(:artifact_registry_ui)

2. As a user who belongs to an organization, visit /o/<organization_path>/-/settings/artifact_registry.
3. The settings page mounts and renders the Activation section - its title and description - with no body content yet (monolith/S10 adds the body).

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist.

Related to #604734 (closed)