fix: style select input in settings, fix user name placeholder

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/locales/ar.json

@@ -171,6 +171,7 @@
     "users": "المستخدمون",
     "usersHint": "أضف مستخدمين برمز PIN. المشاهدون يمكنهم رؤية لوحة التحكم فقط.",
     "userName": "الاسم",
+    "userNamePlaceholder": "مثال: أحمد",
     "userPin": "رمز PIN",
     "userRole": "الدور"
   },

src/locales/en.json

@@ -171,6 +171,7 @@
     "users": "Users",
     "usersHint": "Add users with a PIN code. Viewers can see the dashboard but not settings.",
     "userName": "Name",
+    "userNamePlaceholder": "e.g. Ahmed",
     "userPin": "PIN",
     "userRole": "Role"
   },