Update email notification before/after vendor connection expired

**Background**
When a vendor connection expires, its row is removed from the third-party connection table. To reconnect, users must log in again from the vendor application and re-authenticate from our application. Because this is a heavier action than extending, we are adding a second notification 7 days before expiry to increase the chance users act before the connection is lost.

Currently, users receive a single notification 30 days prior to expiry. This ticket adds a second notification at 7 days, and updates copy across the notification set so it is consistent with the "Extend" action in the interface.

**Email updates:**
1. 30-day pre-expiry email — wording update
Given a connection is 30 days from expiry, when the notification email is sent, then the copy reads to align with the "Extend" action shown in the interface (e.g., "To prevent a disruption in service, please log in to extend this connection.")

2. New 7-day pre-expiry email
Given a connection is 7 days from expiry and has not been extended, when the notification is due, then a new email sends using a template similar to the 30-day email.

3. Post-expiry notification — remove "renew" language
Given a connection has expired and its row has been removed from the table, when the expiry notification sends, then the copy no longer references "renewing" the connection.

Figma link
https://www.figma.com/design/hYr839ZPCXmPDQryyZoPmE/API-Affiliation?node-id=2365-10564&t=hHkArbQ9F9Baut9r-4