Allow renewal of expired subscriptions

🔍 Problem Statement
As a business owner of a print publication with non-auto-renew subscribers, I can't renew a subscription once it has expired, so I have to create a new one, which skews renewal and churn metrics and print fulfillment lists. This affects every publisher using the invoice-pay or check-pay renewal model, which is standard for regional magazines, trade publications, newsletters and journals.

💡 User Story
As a business owner, I want expired subscriptions to be renewable, so that they're recorded as renewals of the same subscription rather than new subscriptions.

🎯 Definition of Done (DoD)
✔ Admins (from the dashboard) and subscribers (from their account) can renew an expired subscription.
✔ The renewal continues the same subscription record and is reported as a renewal, not a new subscription.
✔ This change will impact the Dashboard, UI and API, specifically the renew subscription action.