fix(KB-239): resolve dropdown z-index stacking issue

- Increase dropdown z-index from 50 to 500 in dashboard styles
- Fixes dropdown being obscured by overlapping elements with higher z-index
- Ensures dropdown menu renders above all page content

packages/dashboard/app/styles.css

@@ -2314,7 +2314,7 @@ body {
   display: flex;
   flex-direction: column;
   gap: 10px;
-  z-index: 50;
+  z-index: 500;
   box-shadow: var(--shadow);
 }