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/i18n/messages/en.json

@@ -44,6 +44,28 @@
     "sustainable": "Sustainable",
     "sustainableDesc": "Ethically sourced ingredients and eco-friendly packaging for a better planet."
   },
+  "Popup": {
+    "badge": "FREE GUIDE",
+    "title": "Join 15,000+ Women Who Transformed Their Skin",
+    "subtitle": "Get Our Free Guide: The Natural Oil Secrets Top Beauty Experts Swear By",
+    "bullets": [
+      "The #1 oil mistake that damages hair (and the simple fix)",
+      "3 oils that reverse aging skin in 30 days",
+      "The 'morning glow' routine celebrities use daily",
+      "The ingredient blacklist you should NEVER use"
+    ],
+    "firstNamePlaceholder": "Enter your first name",
+    "emailPlaceholder": "Enter your email",
+    "ctaButton": "Send Me The Free Guide »",
+    "privacyNote": "No spam. Unsubscribe anytime.",
+    "successTitle": "Success! Check your inbox now!",
+    "successMessage": "The guide has been sent! Check your email (and spam folder) for your free guide.",
+    "alreadySubscribedTitle": "You're already a member!",
+    "alreadySubscribed": "You're already in! Check your email for the guide.",
+    "errorTitle": "Something went wrong",
+    "errorMessage": "We couldn't send the guide. Please try again.",
+    "tryAgain": "Try again"
+  },
   "Products": {
     "collection": "Our Collection",
     "allProducts": "All Products",