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>

packages/ui/src/components/Button.test.tsx

@@ -0,0 +1,31 @@
+import { describe, expect, it, afterEach } from "vitest";
+import { render, screen, cleanup } from "@testing-library/react";
+import { Button } from "./Button.js";
+
+afterEach(() => {
+  cleanup();
+});
+
+describe("Button", () => {
+  it("should render children", () => {
+    render(<Button>Click me</Button>);
+    expect(screen.getByRole("button")).toHaveTextContent("Click me");
+  });
+
+  it("should apply variant styles", () => {
+    render(<Button variant="danger">Delete</Button>);
+    const button = screen.getByRole("button");
+    expect(button.className).toContain("bg-red-600");
+  });
+
+  it("should apply size styles", () => {
+    render(<Button size="lg">Large Button</Button>);
+    const button = screen.getByRole("button");
+    expect(button.className).toContain("px-6");
+  });
+
+  it("should pass through additional props", () => {
+    render(<Button disabled>Disabled</Button>);
+    expect(screen.getByRole("button")).toBeDisabled();
+  });
+});