feat(docs): add documentation site and demo features

- Introduced a new documentation site for Cursor BYOK using Next.js and Fumadocs.
- Added a product demo page with a corresponding Vite configuration.
- Implemented a demo API to simulate LLM calls and responses.
- Enhanced the Makefile to include new build and development commands for the documentation.
- Updated package.json scripts for building and running the documentation site.
- Created various components and layouts for the documentation structure, including blog and user documentation sections.
- Added styling for the new components and layouts to ensure a cohesive design.
- Included a README and other necessary files for local development and deployment.

apps/docs/app/(home)/layout.tsx

@@ -0,0 +1,6 @@
+import { HomeLayout } from 'fumadocs-ui/layouts/home';
+import { baseOptions } from '@/lib/layout.shared';
+
+export default function Layout({ children }: LayoutProps<'/'>) {
+  return <HomeLayout {...baseOptions()}>{children}</HomeLayout>;
+}