Polish admin and stats tab styling

Improve tab border handling and spacing for admin and stats views, plus minor copy spacing fixes.

public/css/app.css

@@ -626,6 +626,7 @@ footer {
     padding: 0;
     margin-top: -1px;
     padding-top: 0 !important;
+    border-top: 1px solid var(--app-border);
   }
 
   /* Hide top border under the active admin tab */
@@ -638,13 +639,17 @@ footer {
     position: absolute;
     top: 0;
     left: 0;
-    height: 1px;
+    height: 2px;
     width: calc(100% + 2px);
     margin-left: -1px;
-    background: transparent;
+    background: var(--app-surface);
     pointer-events: none;
   }
 
+  #adminTabs + .admin-tabs-content > .tab-pane.fade::before {
+    background: transparent;
+  }
+
   #adminTabs + .admin-tabs-content .tab-pane .card:first-of-type {
     border-top-color: transparent;
   }