feat: add brand page

[Adebesin-Cell]

This PR adds a dedicated /brand page for press, media, and community use, taking inspiration from Nuxt’s design kit and IQ Wiki’s branding page.

What’s included

• Logo showcase
  A full set of logo variants (wordmark, mark), displayed on both light and dark backgrounds, with quick SVG and PNG downloads.

• Customize your logo
  An interactive preview where you can adjust the accent color and toggle between light/dark backgrounds. You can download the customized logo as SVG or PNG, with all colors baked in (no CSS variables).

• Color palette
  Core brand colors (Background, Foreground, Accent) with one-click copy for both HEX and OKLch values, plus screen reader-friendly aria-live feedback.

• Typography specimens
  Geist Sans and Geist Mono are shown across multiple sizes, including pangrams and number samples.

• Usage guidelines
  Clear do’s and don’ts to help people use the logo correctly.

• Header logo context menu
  Right-click the header logo anywhere in the app to quickly “Copy logo as SVG” or jump to the brand kit, mirroring the pattern from nuxt.com.

Media

Screen.Recording.2026-03-22.at.17.52.14.mov