Responsive Contact Form Integration -- 2

I have the front-end designs ready and now need a working contact form that drops straight into my existing codebase. The form must be fully responsive so it behaves flawlessly on both desktop browsers and, in particular, on Android devices—which is where most of my visitors come from. When a visitor submits, the data (plus any attached file) should be sent to my Gmail account. I’m fine with whatever back-end language you prefer—PHP, Node, or another—so long as you configure it to use Gmail securely (OAuth2 or App Password, no plain SMTP credentials in the repo). Deliverables • Clean, commented HTML/CSS/JS files that match my current styling • Server-side script configured for Gmail email delivery • File-upload field with size/type validation • Clear integration notes so I can drop the form into my site without hunting for dependencies • Final build tested on Android and one desktop browser, with screenshots or a short screen-capture proving responsiveness and successful email delivery Let me know if you need a preview link to the existing layout or any additional assets.