feat: update header logos for light and dark modes

- Light mode: bmad-light.png (dark blue background with lightning)
- Dark mode: bmad-dark.png (light background variant)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

website/astro.config.mjs

@@ -38,8 +38,8 @@ export default defineConfig({
       tagline: 'AI-driven agile development with specialized agents and workflows that scale from bug fixes to enterprise platforms.',
 
       logo: {
-        light: './public/img/banner-bmad-method2.png',
-        dark: './public/img/banner-bmad-method-dark.png',
+        light: './public/img/bmad-light.png',
+        dark: './public/img/bmad-dark.png',
         alt: 'BMAD Method',
         replacesTitle: true,
       },