feat(#1): Set up monorepo scaffold with pnpm workspaces + TurboRepo

Implements the foundational project structure including:
- pnpm workspaces configuration
- TurboRepo for build orchestration
- NestJS 11.1.12 API (apps/api)
- Next.js 16.1.6 web app (apps/web)
- Shared packages (config, shared, ui)
- TypeScript strict mode configuration
- ESLint + Prettier setup
- Vitest for unit testing (19 passing tests)

Fixes #1

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

apps/api/src/app.controller.test.ts

@@ -0,0 +1,31 @@
+import { describe, expect, it } from "vitest";
+import { AppService } from "./app.service";
+import { AppController } from "./app.controller";
+
+describe("AppController", () => {
+  const appService = new AppService();
+  const controller = new AppController(appService);
+
+  describe("getHello", () => {
+    it('should return "Mosaic Stack API"', () => {
+      expect(controller.getHello()).toBe("Mosaic Stack API");
+    });
+  });
+
+  describe("getHealth", () => {
+    it("should return health status", () => {
+      const result = controller.getHealth();
+      expect(result.success).toBe(true);
+      expect(result.data.status).toBe("healthy");
+      expect(result.data.timestamp).toBeDefined();
+    });
+  });
+});
+
+describe("AppService", () => {
+  const service = new AppService();
+
+  it('should return "Mosaic Stack API"', () => {
+    expect(service.getHello()).toBe("Mosaic Stack API");
+  });
+});