feat(lifecycle): add billing lifecycle with auto-suspend/delete

- New AppLifecycleService with cron-based scanner (60s interval)
- State machine: ACTIVE → SUSPENDED → PENDING_DELETION → DELETED
- Auto-renew hourly plans from wallet
- Admin-configurable grace periods via PlatformSettings table
- New LifecycleController (GET/PATCH /lifecycle/settings)
- PlatformSetting entity for runtime admin config
- BillingService: calculateCostForApp, deductWallet
- Application entity: planId, billingCycle, lifecycleStatus, planExpiresAt
- New enums: AppLifecycleStatus, BillingCycle

backend/src/common/enums.ts

@@ -80,3 +80,12 @@ export enum TransactionType {
   DEDUCTION = 'deduction', // Payment for service
   REFUND = 'refund',       // Refund
 }
+
+// ── Application Lifecycle ─────────────────────────────
+
+export enum AppLifecycleStatus {
+  ACTIVE = 'active',               // Paid & running
+  SUSPENDED = 'suspended',         // Plan expired, pods scaled to 0, data retained
+  PENDING_DELETION = 'pending_deletion', // Grace period — will be deleted if no payment
+  DELETED = 'deleted',             // Fully removed from K8s and DB
+}