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/billing/billing.module.ts

@@ -1,4 +1,4 @@
-import { Module } from '@nestjs/common';
+import { Module, forwardRef } from '@nestjs/common';
 import { TypeOrmModule } from '@nestjs/typeorm';
 import { BillingService } from './billing.service';
 import { BillingController } from './billing.controller';
@@ -6,10 +6,13 @@ import { ServicePlan } from './entities/service-plan.entity';
 import { PricingRule } from './entities/pricing-rule.entity';
 import { Wallet } from './entities/wallet.entity';
 import { WalletTransaction } from './entities/wallet-transaction.entity';
+import { PlatformSetting } from './entities/platform-setting.entity';
+import { LifecycleModule } from '../lifecycle/lifecycle.module';
 
 @Module({
   imports: [
-    TypeOrmModule.forFeature([ServicePlan, PricingRule, Wallet, WalletTransaction]),
+    TypeOrmModule.forFeature([ServicePlan, PricingRule, Wallet, WalletTransaction, PlatformSetting]),
+    forwardRef(() => LifecycleModule),
   ],
   controllers: [BillingController],
   providers: [BillingService],