feat(popup): add email capture popup with Mautic integration

- Email capture popup with scroll (10%) and exit intent triggers
- First name field and full tracking (UTM, device, time on page)
- Mautic API integration for contact creation
- GeoIP detection for country/region
- 4 locale support (sr, en, de, fr)
- Mautic tracking script in layout

src/hooks/useScrollDepth.ts

@@ -0,0 +1,28 @@
+"use client";
+
+import { useEffect, useState } from "react";
+
+export function useScrollDepth(threshold: number = 20): boolean {
+  const [hasReachedThreshold, setHasReachedThreshold] = useState(false);
+
+  useEffect(() => {
+    const handleScroll = () => {
+      if (hasReachedThreshold) return;
+      
+      const scrollTop = window.scrollY || document.documentElement.scrollTop;
+      const docHeight = document.documentElement.scrollHeight - window.innerHeight;
+      const scrollPercent = docHeight > 0 ? (scrollTop / docHeight) * 100 : 0;
+      
+      if (scrollPercent >= threshold) {
+        setHasReachedThreshold(true);
+      }
+    };
+
+    window.addEventListener("scroll", handleScroll, { passive: true });
+    handleScroll();
+    
+    return () => window.removeEventListener("scroll", handleScroll);
+  }, [threshold, hasReachedThreshold]);
+
+  return hasReachedThreshold;
+}