Paid Newsletter and plans: Improve status and prorata

Context: https://github.com/Automattic/jpop-issues/issues/9282#issuecomment-2445527662

## Ideas mentioned
- [ ] Add a history of deleted/old plans in the Tools » Monetize » Payment Settings option. Or add a label with `Active` or `Archived` (or something similar) so the status is clear.
- [ ] Improve the modal, mainly the wording:
- 
- [ ] Provide more information about prorata cases to the site owner. [See this comment](https://github.com/Automattic/jpop-issues/issues/9282#issuecomment-2446469533). As Fab mentions: "Maybe "prorated price from previous subscription" will be better than "discount". Also letting the content-creator know in the receipt next to "earnings" could be helpful."

Start in Tools » Monetize » Payment Settings and read the linked context issue for the plan and prorata details. Trace the status display, modal wording, and receipt or earnings information, then verify that active or archived plans and prorated pricing are clearly communicated.

Written by the indexing model from the issue text.