リロード不要！Server Actionsで即フォーム送信

Create a single HTML file with embedded CSS and JS that demonstrates a Next.js-like Server Actions form submission using a simple mock server. The form should have fields for name and email, and submit without page reload, showing a loading state and success/error messages. Use only vanilla JavaScript (no framework) but style it with Tailwind CSS via CDN. The mock server should simulate a 1.5 second delay and return a success response.