Vantix Footer — Référence de design web et prompt

# Prompt: Vantix footer ("Cobalt Flare")

Build a single-file **website footer** for a fictional creative agency, **Vantix**. Use plain HTML, CSS, inline SVG and vanilla JS, with no framework and no build step. The look is a deep-navy footer under a glowing electric cobalt and cyan aurora band. A thin blue arc runs through a glowing glass ring, and a big vertical cyan wordmark stands between two hairline dividers, with link columns, a "Book a call" call to action and social icons.