fix: resolve HTML hierarchy, accessibility and PDF link issues

- Fix heading level skip in ContactContent success state (H3 -> H2)
- Clean up deprecated iframe attributes in ContactContent
- Add aria-label to footer logo link for WCAG compliance
- Rename PDF assets to hyphenated filenames to fix link checks
- Update AGB page with new PDF link format

components/ContactContent.tsx

@@ -162,13 +162,8 @@ export default function Contact() {
                 <div className="w-full h-[300px] rounded-[2.5rem] overflow-hidden border border-white/10 shadow-sm grayscale hover:grayscale-0 transition-all duration-700 relative group">
                   <div className="absolute inset-0 border-2 border-accent/0 group-hover:border-accent/20 transition-all duration-500 z-10 pointer-events-none rounded-[2.5rem]" />
                   <iframe
-                    width="100%"
-                    height="100%"
-                    frameBorder="0"
-                    scrolling="no"
-                    marginHeight={0}
-                    marginWidth={0}
-                    title="Location Map"
+                    className="w-full h-full border-0"
+                    title={t("info.mapTitle") || "Location Map"}
                     src="https://www.openstreetmap.org/export/embed.html?bbox=9.445,48.815,9.465,48.825&layer=mapnik&marker=48.8198,9.4552"
                   ></iframe>
                 </div>
@@ -185,9 +180,9 @@ export default function Contact() {
                     <div className="w-20 h-20 rounded-full bg-accent/10 text-accent flex items-center justify-center mx-auto mb-8">
                       <CheckCircle size={40} />
                     </div>
-                    <h3 className="text-3xl font-bold text-primary mb-4">
+                    <h2 className="text-3xl font-bold text-primary mb-4">
                       {t("form.successTitle")}
-                    </h3>
+                    </h2>
                     <p className="text-slate-600 text-lg mb-10">
                       {t("form.successMessage")}
                     </p>