Expired memberships counted for purposes of getting active focus

### Steps to reproduce

We seem to count expired memberships for the purpose of determining the active focus. We should filter them before this point.

### Outcome

#### What did you expect?

#### What happened instead?

### Operating system

_No response_

### Browser information

_No response_

### URL for webapp

_No response_

### Will you send logs?

No

The issue names no files, tests, or entry points. Start by locating the logic that determines active focus and filters memberships, then reproduce the expired-membership case and add coverage showing that expired memberships are excluded.

Written by the indexing model from the issue text.