docs(design): remove SVG, use PNG logo only

SVG icon is no longer in use. public/logo.png (1024x1024 RGBA) is
the single logo asset. DESIGN.md updated accordingly: SVG snippet
removed, wordmark pattern and <head> references updated to PNG.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

node_modules/tailwindcss/colors.js

@@ -0,0 +1,2 @@
+let colors = require('./lib/public/colors')
+module.exports = (colors.__esModule ? colors : { default: colors }).default