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

components/ContactForm.tsx

@@ -148,7 +148,6 @@ export default function ContactForm() {
             autoComplete="name"
             enterKeyHint="next"
             onFocus={() => handleFocus('contact-name')}
-            aria-label={t('form.name')}
             required
           />
         </div>
@@ -163,7 +162,6 @@ export default function ContactForm() {
             enterKeyHint="next"
             placeholder={t('form.emailPlaceholder')}
             onFocus={() => handleFocus('contact-email')}
-            aria-label={t('form.email')}
             required
           />
         </div>
@@ -176,7 +174,6 @@ export default function ContactForm() {
             enterKeyHint="send"
             placeholder={t('form.messagePlaceholder')}
             onFocus={() => handleFocus('contact-message')}
-            aria-label={t('form.message')}
             required
           />
         </div>