fix(ui): increase main content top padding for better visual balance

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/css/layout/app-shell.css

@@ -419,7 +419,7 @@
 
     .app-main-content {
       padding-inline: calc(var(--app-spacing) * 2);
-      padding-block-start: var(--app-spacing);
+      padding-block-start: calc(var(--app-spacing) * 2);
       margin-bottom: calc(var(--app-spacing) * 2);
     }
     .app-main-content:has(.app-details-container) {