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>

frontend/src/types/index.ts

@@ -144,6 +144,25 @@ export type DeploymentStatus =
 
 export type AppLifecycleStatus = 'active' | 'suspended' | 'pending_deletion' | 'deleted';
 
+export interface ResourceCredit {
+  id: string;
+  sourceAppName?: string;
+  runtime: string;
+  databaseType: string;
+  cpuLimit: string;
+  memoryLimit: string;
+  replicas: number;
+  dbStorageSize?: string;
+  appStorageSize?: string;
+  enableRedis: boolean;
+  enableRabbitmq: boolean;
+  enableElasticsearch: boolean;
+  billingCycle?: string;
+  expiresAt: string;
+  remainingMs: number;
+  remainingLabel: string;
+}
+
 export interface Cluster {
   id: string;
   name: string;
@@ -399,6 +418,25 @@ export interface CostBreakdown {
   breakdown: { label: string; hourly: number; monthly: number; yearly: number }[];
 }
 
+export interface DeployExtraChargeLine {
+  label: string;
+  amount: number;
+  fullPeriodAmount?: number;
+}
+
+export interface DeployCostPreview extends CostBreakdown {
+  cycle: BillingCycle;
+  fullAmount: number;
+  amountDue: number;
+  coveredAmount: number;
+  waivedAmount: number;
+  extrasBreakdown: DeployExtraChargeLine[];
+  creditApplied: ResourceCredit | null;
+  prepaidCreditUsed: boolean;
+  prorateRemainingDays?: number;
+  proratePeriodDays?: number;
+}
+
 // ─── Snapshot / Rollback types ──────────────────────
 
 export type SnapshotType = 'pre_deploy' | 'manual';