chore: README glow-up — gradient hero banner

[brentrager]

Bolder, less-bland take on the Smoo AI README brand (frontend-design aesthetic): a custom gradient hero banner (brand mesh: warm orange→red glow → teal, glowing S mark, bold display wordmark, gradient accent rule, "AI built into every product" kicker) shipped as a crisp 2× PNG (.github/banner.png, SVG source kept), plus punchier for-the-badge primary badges and a bolder nav. All content preserved.

This is the exemplar — if the direction looks good, I'll fan the same treatment out to all the other repos. Banner is generated from a parametric template so each repo gets its own name/tagline.

🤖 Generated with Claude Code

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Latest commit: ca5a548

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