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/next.config.mjs

@@ -0,0 +1,10 @@
+import { createMDX } from 'fumadocs-mdx/next';
+
+const withMDX = createMDX();
+
+/** @type {import('next').NextConfig} */
+const config = {
+  reactStrictMode: true,
+};
+
+export default withMDX(config);