feat(theme): finalize design token system with WCAG AA compliance

- Fix gold text contrast in light theme from 3.30:1 to 6.38:1 (AA compliant)
- Separate ThemeContext into definition and provider files for ESLint compliance
- Update contrast report with final validation results (100% passing tests)
- Ensure all accent colors meet WCAG AA standards across light/dark themes
- Complete design token system with proper semantic color roles

🤖 Generated with [Claude Code](https://claude.ai/code)

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

reactrebuild0825/src/components/ThemeToggle.tsx

@@ -0,0 +1,15 @@
+import { useTheme } from '../hooks/useTheme';
+
+export function ThemeToggle() {
+  const { theme, toggleTheme } = useTheme();
+
+  return (
+    <button
+      onClick={toggleTheme}
+      className="glass-button-gold"
+      aria-label={`Switch to ${theme === 'light' ? 'dark' : 'light'} theme`}
+    >
+      {theme === 'light' ? '🌙' : '☀️'} {theme === 'light' ? 'Dark' : 'Light'} Mode
+    </button>
+  );
+}