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/config/orchestrator.config.ts

@@ -0,0 +1,26 @@
+import { registerAs } from "@nestjs/config";
+
+export const orchestratorConfig = registerAs("orchestrator", () => ({
+  port: parseInt(process.env.ORCHESTRATOR_PORT ?? "3001", 10),
+  valkey: {
+    host: process.env.VALKEY_HOST ?? "localhost",
+    port: parseInt(process.env.VALKEY_PORT ?? "6379", 10),
+    url: process.env.VALKEY_URL ?? "redis://localhost:6379",
+  },
+  claude: {
+    apiKey: process.env.CLAUDE_API_KEY,
+  },
+  docker: {
+    socketPath: process.env.DOCKER_SOCKET ?? "/var/run/docker.sock",
+  },
+  git: {
+    userName: process.env.GIT_USER_NAME ?? "Mosaic Orchestrator",
+    userEmail: process.env.GIT_USER_EMAIL ?? "orchestrator@mosaicstack.dev",
+  },
+  killswitch: {
+    enabled: process.env.KILLSWITCH_ENABLED === "true",
+  },
+  sandbox: {
+    enabled: process.env.SANDBOX_ENABLED === "true",
+  },
+}));