Staging Sites: Update primary button text on staging sites

### What

Let's update the text in the button to be consistent with the production site.
In the production tab we say "Manage staging site" and in the staging tab we say Switch to production. Let's use the same verb in both places. Probably manage makes more sense.

### Why

During the Server Settings Walkthrough, we identified the opportunity to update the staging .

pesfPa-1n1-p2

### How

_No response_

Locate the staging-site UI that renders the production and staging tabs, then find the two primary button labels shown in the issue. Confirm the staging-tab action uses the same “Manage” verb as the production tab, and verify both labels in the walkthrough or staging-site interface.

Written by the indexing model from the issue text.