Migrate Organizations app entrypoints to Vue 3

What does this MR do?

Rolls out Vue 3 (via @vue/compat, Option 1 of the Vue 3 migration guide) for the Organizations app page entrypoints, the organization groups and projects pages, and the admin Organizations index and settings pages. This is a rollout mechanism only — no Vue components were rewritten. Each entrypoint gets a vue3_migration.yml so the bundler builds both a Vue 2 and a Vue 3 chunk; Rails serves the Vue 3 chunk only when the feature flag is enabled.

Migrated entrypoints

• app/assets/javascripts/pages/organizations/organizations/index
• app/assets/javascripts/pages/organizations/organizations/new
• app/assets/javascripts/pages/organizations/organizations/show
• app/assets/javascripts/pages/organizations/organizations/activity
• app/assets/javascripts/pages/organizations/organizations/groups_and_projects
• app/assets/javascripts/pages/organizations/organizations/users
• app/assets/javascripts/pages/organizations/groups/new
• app/assets/javascripts/pages/organizations/groups/edit
• app/assets/javascripts/pages/organizations/projects/edit
• app/assets/javascripts/pages/admin/organizations/settings/general
• ee/app/assets/javascripts/pages/admin/organizations/index (EE-only)

Feature flag

Gated behind vue3_migrate_organizations (type: beta, default_enabled: false). Vue 2 remains the default until the flag is enabled.

Verification

• node scripts/frontend/codemods/vue3_init_vue_app.mjs --list <entrypoints> reports No residual sites — every entrypoint delegates to an init* function rather than a raw new Vue({ el, render }) root mount, so no initVueApp conversion is needed.
• The flag YAML parses and all 11 vue3_migration.yml files pass config/vue3migration/migration_schema.js and spec/lib/gitlab/vue3_migration_files_spec.rb.

No genuine logic regressions were found independent of the compat flags.

Closes #608124 (closed)