chore: achieve 100/100 pagespeed and html validation

- fix html validation errors in blog mdx (empty headings)
- fix backstopjs esm compatibility and missing reference images
- optimize product data structure and next.config.mjs
- finalize accessibility and seo improvements

backstop_data/engine_scripts/puppet/onReady.cjs

@@ -0,0 +1,20 @@
+/* eslint-disable */
+module.exports = async (page, scenario, vp) => {
+  console.log('SCENARIO > ' + scenario.label);
+
+  // Disable CSS animations instantly to avoid flaky screenshots
+  await page.evaluate(() => {
+    const style = document.createElement('style');
+    style.innerHTML = `
+      * {
+        animation: none !important;
+        transition: none !important;
+        caret-color: transparent !important;
+      }
+    `;
+    document.head.appendChild(style);
+  });
+
+  // Example: Wait for fonts to load
+  await page.evaluate(() => document.fonts.ready);
+};