feat(01-01): NestJS API with health endpoint and Prisma schema

- NestJS app with ConfigModule and HealthModule
- GET /health endpoint returning {status, timestamp} using HealthResponse type
- Prisma schema with PostgreSQL datasource and Tenant model (multi-tenancy foundation)
- Multi-stage Dockerfile with non-root nestjs user, monorepo root as build context
- Workspace dependency on @tessera/shared for shared types
- Type-check passes successfully

apps/api/src/app.module.ts

@@ -0,0 +1,11 @@
+import { Module } from '@nestjs/common';
+import { ConfigModule } from '@nestjs/config';
+import { HealthModule } from './health/health.module';
+
+@Module({
+  imports: [
+    ConfigModule.forRoot({ isGlobal: true }),
+    HealthModule,
+  ],
+})
+export class AppModule {}

apps/api/src/health/health.controller.ts

@@ -0,0 +1,13 @@
+import { Controller, Get } from '@nestjs/common';
+import type { HealthResponse } from '@tessera/shared';
+
+@Controller('health')
+export class HealthController {
+  @Get()
+  check(): HealthResponse {
+    return {
+      status: 'ok',
+      timestamp: new Date().toISOString(),
+    };
+  }
+}

apps/api/src/health/health.module.ts

@@ -0,0 +1,7 @@
+import { Module } from '@nestjs/common';
+import { HealthController } from './health.controller';
+
+@Module({
+  controllers: [HealthController],
+})
+export class HealthModule {}

apps/api/src/main.ts

@@ -0,0 +1,13 @@
+import { NestFactory } from '@nestjs/core';
+import { AppModule } from './app.module';
+
+async function bootstrap() {
+  const app = await NestFactory.create(AppModule);
+
+  app.enableCors({ origin: true });
+
+  await app.listen(3001);
+  console.log('Tessera API running on port 3001');
+}
+
+bootstrap();