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/web/src/app/page.test.tsx

@@ -0,0 +1,22 @@
+import { describe, expect, it, afterEach } from "vitest";
+import { render, screen, cleanup } from "@testing-library/react";
+import Home from "./page";
+
+afterEach(() => {
+  cleanup();
+});
+
+describe("Home", () => {
+  it("should render the title", () => {
+    render(<Home />);
+    expect(screen.getByRole("heading", { level: 1 })).toHaveTextContent("Mosaic Stack");
+  });
+
+  it("should render the buttons", () => {
+    render(<Home />);
+    const buttons = screen.getAllByRole("button");
+    expect(buttons.length).toBe(2);
+    expect(buttons[0]).toHaveTextContent("Get Started");
+    expect(buttons[1]).toHaveTextContent("Learn More");
+  });
+});