Add hero section to home page with scroll collapse

- Full-screen dark gradient hero on home page
- Search input centered vertically
- Smooth collapse to fixed header on scroll
- Added hero translations (ru/en)

i18n/locales/en/hero.json

@@ -0,0 +1,6 @@
+{
+  "hero": {
+    "title": "Wholesale Trading",
+    "subtitle": "Find the best suppliers and products"
+  }
+}

i18n/locales/ru/hero.json

@@ -0,0 +1,6 @@
+{
+  "hero": {
+    "title": "Оптовая торговля",
+    "subtitle": "Найдите лучших поставщиков и товары"
+  }
+}