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/lib/blog.ts

@@ -0,0 +1,35 @@
+import { loader } from 'fumadocs-core/source';
+import { pageSchema } from 'fumadocs-core/source/schema';
+import { defineCollections } from 'fumadocs-mdx/macro';
+
+const blog = defineCollections({
+  type: 'doc',
+  dir: 'content/blog',
+  schema: pageSchema,
+});
+
+export const blogSource = loader({
+  baseUrl: '/blog',
+  source: blog.toFumadocsSource(),
+});
+
+export function getBlogDate(path: string): Date {
+  const fileName = path.split('/').at(-1) ?? '';
+  const match = /^(\d{4}-\d{2}-\d{2})/.exec(fileName);
+  return match ? new Date(`${match[1]}T00:00:00Z`) : new Date(0);
+}
+
+export function formatBlogDate(path: string): string {
+  return new Intl.DateTimeFormat('zh-CN', {
+    year: 'numeric',
+    month: 'long',
+    day: 'numeric',
+    timeZone: 'UTC',
+  }).format(getBlogDate(path));
+}
+
+export function sortBlogPages<T extends { path: string }>(pages: T[]): T[] {
+  return [...pages].sort((left, right) => {
+    return getBlogDate(right.path).getTime() - getBlogDate(left.path).getTime();
+  });
+}