Site-Wide Iframe Contact Button

I need a developer who can drop a single floating button onto my WordPress install and have it appear on every page. When a visitor clicks the button, an iframe should slide in (or pop up—whichever is lighter on resources) and load an external contact-form link.

The job is straightforward: supply the code or lightweight plugin, hook it into the theme so it’s global, and confirm that the iframe displays cleanly on desktop, tablet, and mobile. I don’t want the button to block key content, so placement and z-index matters.

Acceptance criteria:
• Floating button visible across the entire site
• Click opens the iframe with the specified contact form link
• No console errors, layout shifts, or conflicts with existing plugins
• Fully responsive and tested on at least one modern browser per device class

Hand me a short install guide or simply push the changes if you have access; either way I expect to be able to reproduce the setup quickly on staging.