fix: keep broker shell styling scoped

apps/frontend/src/styles.css

@@ -81,16 +81,6 @@ a {
   z-index: 1;
 }
 
-.broker-account {
-  display: grid;
-  gap: 24px;
-}
-
-.broker-account__header h1 {
-  font-size: 28px;
-  line-height: 1.2;
-}
-
 .broker-account__workspace {
   display: grid;
   grid-template-columns: minmax(150px, 190px) minmax(0, 1fr);
@@ -126,7 +116,6 @@ a {
 }
 
 @media (max-width: 720px) {
-  .broker-account,
   .broker-account__workspace {
     gap: 16px;
   }