Extra instance subscriptions not cancelled, refunded, or prorated after deletion

### Current Behavior

When an extra hosted/remote instance (beyond the plan allowance) is deleted, the related Stripe subscription is not cancelled.
No refund or proration is applied, and the subscription remains active in Stripe, continuing to generate invoices.
This occurs on both monthly and yearly billing.

### Expected Behavior

- Deleting an extra instance should:
- Cancel the related Stripe subscription.
- Apply proration or a refund if applicable.
- Prevent further invoices for the deleted instance.

### Steps To Reproduce

1. Create a new team.
2. Exceed the instance limit by 1.
3. Confirm in Stripe that a new subscription for the extra instance is created.
4. Advance time by 1 month to complete the first billing cycle.
5. Delete the extra instance from the UI.
6. Advance time by 2 weeks, then in increments up to 1 month.
7. Observe that:
- No refund or proration is applied.
- The subscription remains active in Stripe.
- The subscription will still be invoiced.

### Environment

- FlowFuse version: 2.20
- Node.js version: N/A
- npm version: N/A
- Platform/OS: N/A
- Browser: N/A

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate