Ability to Disable Proration & Allow Manual Charge Control for Offline Clients

🔍 Problem Statement

Pelcro automatically applies proration when a subscription is modified mid-cycle. For offline clients (invoice-based billing), this creates unexpected credits or charges that conflict with manual billing agreements. There is no way to disable proration or control the charge amount during subscription changes.

💡 User Story

As a Pelcro admin managing offline clients, I want the ability to disable proration and manually set the charge amount during subscription changes, so that billing aligns with offline agreements without unexpected adjustments.

🎯 Definition of Done (DoD)

A feature is done when:

✔️ Given a subscription change for an invoice-based client, when an admin disables proration and specifies a manual charge amount, then the subscription is updated without automatic proration and the specified amount is applied to the next invoice.