feat: add Products navigation button to sidebar

- Added new "Products" navigation item in sidebar
- Links to /product page (product listing)
- "Assets" button now links to / (product detail page)
- Added i18n support for "products" label (EN: Products, ZH: 产品)

Navigation structure:
- Assets → / (Product detail page)
- Products → /product (Product listing page)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

components/Sidebar.tsx

@@ -10,7 +10,8 @@ export default function Sidebar() {
   const pathname = usePathname();
 
   const navigationItems = [
-    { icon: "/icon-assets.svg", label: t("nav.assets"), key: "Assets", path: "/product" },
+    { icon: "/icon-assets.svg", label: t("nav.assets"), key: "Assets", path: "/" },
+    { icon: "/icon-lending.svg", label: t("nav.products"), key: "Products", path: "/product" },
     { icon: "/icon-alp.svg", label: t("nav.alp"), key: "ALP", path: "/alp" },
     { icon: "/icon-swap.svg", label: t("nav.swap"), key: "Swap", path: "/swap" },
     { icon: "/icon-lending.svg", label: t("nav.lending"), key: "Lending", path: "/lending" },