feat: implement locale-aware routing with [locale] dynamic segments

WARNING: This change breaks existing SEO URLs for Serbian locale.

Changes:
- Migrated from separate locale folders (src/app/en/, src/app/de/, etc.)
  to [locale] dynamic segments (src/app/[locale]/)
- Serbian is now at /sr/ instead of / (root)
- English at /en/, German at /de/, French at /fr/
- All components updated to generate locale-aware links
- Root / now redirects to /sr (307 temporary redirect)

SEO Impact:
- Previously indexed Serbian URLs (/, /products, /about, /contact)
  will now return 404 or redirect to /sr/* URLs
- This is a breaking change for SEO - Serbian pages should ideally
  remain at root (/) with only non-default locales getting prefix
- Consider implementing 301 redirects from old URLs to maintain
  search engine rankings

Technical Notes:
- next-intl v4 with [locale] structure requires ALL locales to
  have the prefix (cannot have default locale at root)
- Alternative approach would be separate folder structure per locale

src/components/home/Hero.tsx

@@ -2,8 +2,10 @@
 
 import { motion } from "framer-motion";
 import Link from "next/link";
+import { useLocale } from "next-intl";
 
 export default function Hero() {
+  const locale = useLocale();
   return (
     <section className="relative h-screen min-h-[600px] flex items-center justify-center overflow-hidden">
       <div className="absolute inset-0 bg-gradient-to-b from-background-ice/50 to-background" />
@@ -48,7 +50,7 @@ export default function Hero() {
           transition={{ duration: 0.8, delay: 0.8 }}
         >
           <Link
-            href="/en/products"
+            href={`/${locale}/products`}
             className="inline-block px-10 py-4 bg-foreground text-white text-lg tracking-wide hover:bg-accent-dark transition-colors duration-300"
           >
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