Implemented phase 3 for the POC prototype in the Website service.

Services/Website/Sources/Library/Internal/Components/SiteHeader.swift

@@ -203,11 +203,13 @@ private extension SiteHeader {
             unit: "unread",
             path: .Route.messages
         )
-        a(
-            .class("site-header__text-link site-header__text-link--strong from-desktop"),
-            .href(.Route.sellerDashboard)
-        ) {
-            "My shop"
+        if viewer.hasShop {
+            a(
+                .class("site-header__text-link site-header__text-link--strong from-tablet"),
+                .href(.Route.sellerDashboard)
+            ) {
+                "My shop"
+            }
         }
         a(
             .class("site-header__account"),