Set Admin search by email

[balebbae]

Description

Add email search functionality to the Set Admin input on the super admin page, with a corresponding backend query to look up users by email.

Requirements

• Add a search/lookup input on the super admin page that allows searching for users by email
• Implement a backend query/endpoint to look up users by email address
• Wire the frontend Set Admin input to use the new email search
• Return matching user results so the super admin can select and assign admin roles

Acceptance Criteria

• Backend query to search users by email is implemented
• Super admin page Set Admin input supports email search
• Search results display matching users for selection