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/package.json

@@ -0,0 +1,39 @@
+{
+  "name": "cursor-byok-docs",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "build:product-demo": "node scripts/build-product-demo.mjs",
+    "prebuild": "npm run build:product-demo",
+    "build": "next build",
+    "predev": "npm run build:product-demo",
+    "dev": "next dev",
+    "start": "next start",
+    "types:check": "next typegen && tsc --noEmit",
+    "lint": "eslint",
+    "check": "npm run types:check && npm run lint && npm run build"
+  },
+  "dependencies": {
+    "@fumadocs/language": "^0.2.4",
+    "cnfast": "^0.1.0",
+    "fumadocs-core": "16.15.2",
+    "fumadocs-mdx": "15.3.1",
+    "fumadocs-ui": "npm:@fumadocs/base-ui@16.15.2",
+    "lucide-react": "^1.34.0",
+    "next": "16.3.2",
+    "react": "^19.2.8",
+    "react-dom": "^19.2.8"
+  },
+  "devDependencies": {
+    "@tailwindcss/postcss": "^4.3.3",
+    "@types/mdx": "^2.0.14",
+    "@types/node": "^26.3.0",
+    "@types/react": "^19.2.18",
+    "@types/react-dom": "^19.2.5",
+    "eslint": "^9.39.4",
+    "eslint-config-next": "16.3.2",
+    "postcss": "^8.5.26",
+    "tailwindcss": "^4.3.3",
+    "typescript": "^6.0.3"
+  }
+}