fix(seo): resolve pagespeed insights performance and accessibility issues

- Add priority to hero image and replace css background-image with Next.js Image component for faster LCP
- Add aria-label and aria-expanded to mobile menu button in Navbar
- Add aria-label to social media links in Footer
- Replace css background-image with Next.js Image component in CTA and Services sections

app/components/Navbar.tsx

@@ -80,6 +80,8 @@ export default function Navbar({ lang, dict }: { lang: Locale; dict: any }) {
 
           {/* Mobile menu button */}
           <button
+            aria-label={mobileMenuOpen ? "Menüyü kapat" : "Menüyü aç"}
+            aria-expanded={mobileMenuOpen}
             className="md:hidden text-white"
             onClick={() => setMobileMenuOpen(!mobileMenuOpen)}
           >