Add prepaid resource credits with prorated deploy billing.

When users delete an app before plan expiry, remaining resources become credits for a new deploy. The deploy calculator shows covered vs additional charges, prices optional services correctly, and prorates extras to days left on the credit.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/lifecycle/app-lifecycle.service.ts

@@ -54,12 +54,19 @@ export class AppLifecycleService implements OnModuleInit, OnModuleDestroy {
    * Activate or reactivate an application after successful payment.
    * Calculates the new expiry based on billing cycle and scales pods back up.
    */
-  async activateApp(appId: string, billingCycle: BillingCycle, planId: string): Promise<Application> {
+  async activateApp(
+    appId: string,
+    billingCycle: BillingCycle,
+    planId: string,
+    planExpiresAt?: Date,
+  ): Promise<Application> {
     const app = await this.appRepo.findOne({ where: { id: appId } });
     if (!app) throw new Error(`Application ${appId} not found`);
 
     const now = new Date();
-    const expiresAt = this.calculateExpiry(now, billingCycle);
+    const expiresAt = planExpiresAt && planExpiresAt > now
+      ? planExpiresAt
+      : this.calculateExpiry(now, billingCycle);
 
     app.planId = planId;
     app.billingCycle = billingCycle;