Add fonts module: document and load Raleway/Roboto in solid-ui

[Copilot]

style.js referenced Raleway, Roboto, and Arial in inline style strings, but none of these web fonts were ever loaded — Raleway and Roboto silently fell back to the browser's sans-serif on most systems.

Changes

• src/styleConstants.js — two new constants centralise the font stacks:

  fontFamilyButton: 'Raleway, Roboto, sans-serif',
  fontFamilyHeader: 'Arial, sans-serif',

• src/style.js — all hard-coded font-family literals replaced with template-literal references to those constants.

• src/fonts.ts (new) — public module exposing:

  • fontNames — individual font names (Raleway, Roboto)
  • fontFamilies — full CSS font-family stacks
  • loadFonts(url?) — idempotent function that injects a <link rel="stylesheet"> into document.head; defaults to Google Fonts but accepts any self-hosted URL for privacy-conscious deployments:

    // Use default Google Fonts endpoint
    loadFonts()
    
    // Or supply a self-hosted stylesheet
    loadFonts('https://my-pod.example/fonts/raleway-roboto.css')

• src/index.ts — fonts added to named exports and window.UI.

[SharonStrats]

I was just asking a question didn't want a PR.