Refactor: Move Admin Page and Subpages from `/control/admin/` to `/admin/`

[mariobehling]

The current Admin section of the Eventyay platform is located under the path:

https://next.eventyay.com/control/admin/

To simplify the URL structure and align with the unified routing schema, all Admin pages and their subpages should be moved to:

https://next.eventyay.com/admin/

Expected Behavior

• The main admin page should be accessible at:
  https://next.eventyay.com/admin/

• All subpages (e.g., global settings, organizers, users, system settings, etc.) should follow the same structure, for example:

  • https://next.eventyay.com/admin/global/settings/
  • https://next.eventyay.com/admin/organizers/
  • https://next.eventyay.com/admin/users/

• The old URLs under /control/admin/ should redirect to the new structure for backward compatibility.

Tasks

• Update routes and views for the Admin section to use /admin/ base path.
• Update navigation links, breadcrumbs, and menu references.
• Implement 301 redirects from /control/admin/* to /admin/*.
• Verify that all admin subpages remain accessible after migration.
• Update tests and documentation accordingly.

Testing Checklist

• Accessing /control/admin/ redirects correctly to /admin/.
• All subpages under /admin/ load without broken links or missing assets.
• Navigation menus and URLs reflect the updated structure.
• No impact on organizer or user routes.