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/desktop/vite.demo.config.ts

@@ -0,0 +1,22 @@
+import { fileURLToPath } from "node:url";
+import react from "@vitejs/plugin-react";
+import { defineConfig } from "vite";
+import { staticI18nPlugin } from "./plugins/static-i18n-plugin.ts";
+
+const desktopRoot = fileURLToPath(new URL("./", import.meta.url));
+const demoInput = fileURLToPath(new URL("./demo/index.html", import.meta.url));
+const demoOutput = fileURLToPath(new URL("../docs/public/product-demo", import.meta.url));
+
+export default defineConfig({
+  root: desktopRoot,
+  base: "/product-demo/",
+  plugins: [staticI18nPlugin(), react()],
+  publicDir: false,
+  build: {
+    outDir: demoOutput,
+    emptyOutDir: true,
+    rollupOptions: {
+      input: demoInput,
+    },
+  },
+});