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/components/mdx.tsx

@@ -0,0 +1,18 @@
+import defaultMdxComponents from 'fumadocs-ui/mdx';
+import { Step, Steps } from 'fumadocs-ui/components/steps';
+import type { MDXComponents } from 'mdx/types';
+
+export function getMDXComponents(components?: MDXComponents) {
+  return {
+    ...defaultMdxComponents,
+    Step,
+    Steps,
+    ...components,
+  } satisfies MDXComponents;
+}
+
+export const useMDXComponents = getMDXComponents;
+
+declare global {
+  type MDXProvidedComponents = ReturnType<typeof getMDXComponents>;
+}