重构 API 为 8 领域 + 应用层架构

将后端模块拆分为 domains、applications、shared 三层，结算计算器移入 domain 纯函数目录，API 路径与测试保持不变。

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

apps/api/src/shared/prisma/prisma.module.ts

@@ -0,0 +1,9 @@
+import { Global, Module } from '@nestjs/common';
+import { PrismaService } from './prisma.service';
+
+@Global()
+@Module({
+  providers: [PrismaService],
+  exports: [PrismaService],
+})
+export class PrismaModule {}

apps/api/src/shared/prisma/prisma.service.ts

@@ -0,0 +1,13 @@
+import { Injectable, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
+import { PrismaClient } from '@prisma/client';
+
+@Injectable()
+export class PrismaService extends PrismaClient implements OnModuleInit, OnModuleDestroy {
+  async onModuleInit() {
+    await this.$connect();
+  }
+
+  async onModuleDestroy() {
+    await this.$disconnect();
+  }
+}