feat(M6): Set up orchestrator service foundation

Add NestJS-based orchestrator service structure for M6-AgentOrchestration.

Changes:
- Migrate from Express to NestJS architecture
- Add health check endpoint module
- Add placeholder modules: coordinator, git, killswitch, monitor, queue, spawner, valkey
- Update configuration for NestJS
- Update lockfile for new dependencies

This is foundational work for M6-AgentOrchestration milestone.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/orchestrator/src/app.module.ts

@@ -0,0 +1,22 @@
+import { Module } from "@nestjs/common";
+import { ConfigModule } from "@nestjs/config";
+import { BullModule } from "@nestjs/bullmq";
+import { HealthModule } from "./api/health/health.module";
+import { orchestratorConfig } from "./config/orchestrator.config";
+
+@Module({
+  imports: [
+    ConfigModule.forRoot({
+      isGlobal: true,
+      load: [orchestratorConfig],
+    }),
+    BullModule.forRoot({
+      connection: {
+        host: process.env.VALKEY_HOST ?? "localhost",
+        port: parseInt(process.env.VALKEY_PORT ?? "6379"),
+      },
+    }),
+    HealthModule,
+  ],
+})
+export class AppModule {}