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/autoprefixer/lib/hacks/placeholder-shown.js

@@ -0,0 +1,19 @@
+let Selector = require('../selector')
+
+class PlaceholderShown extends Selector {
+  /**
+   * Return different selectors depend on prefix
+   */
+  prefixed(prefix) {
+    if (prefix === '-moz-') {
+      return ':-moz-placeholder'
+    } else if (prefix === '-ms-') {
+      return ':-ms-input-placeholder'
+    }
+    return `:${prefix}placeholder-shown`
+  }
+}
+
+PlaceholderShown.names = [':placeholder-shown']
+
+module.exports = PlaceholderShown