ENH: Manual badge assignment improvements

Two proposed improvements for manual badge assignment, particularly for large sites:

1. Opening the badge assignment page takes several seconds on a large site since it has to retrieve all active portal users. This experience could be improved by some visual feedback.

2. The user page display only uses "display name" which can be duplicated. Add some additional user fields as columns or tooltips. This page is currently only accessible from the Control panel (so only admins see this) so profile visibility shouldn't be a concern.

3. Update assignment date in screen; currently requires refresh