Click-Triggered Popup Contact Form

I need a clean, responsive pop-up contact form that opens only when a visitor clicks a clearly marked button or link. The form has to capture four things:
• Name and Email
• Phone Number
• Message or Inquiry
• Ability to attach a file or image

Please make the modal blend with my existing site style, validate the inputs in real time, and route all submissions to my designated email address (or an endpoint you recommend). I’m happy to work with plain HTML/CSS/JavaScript, a lightweight framework, or a WordPress plugin—whichever delivers the fastest load and smoothest user experience.

Deliverables
1. Fully styled, mobile-friendly pop-up form triggered on click
2. Client-side and server-side validation, including file-size/type limits
3. Email (or API) integration plus a brief setup guide so I can move it to staging and production

Let me know if you need back-end access or prefer a standalone script; I’m flexible on implementation as long as the click-to-open behaviour and the four data points above are handled flawlessly.