- Add /admin/merchant-users/{id}/edit page route and template
- Replace toggle-status button with edit button on merchant-users list
- Editable fields: username, email, first name, last name
- Quick actions: toggle status, delete (with double confirm)
- Move RBAC two-phase plan to docs/proposals/
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
