Support Cmd/Ctrl+click and adaptive bg color

Update the dashboard app tile click handler so Ctrl/Cmd+click opens apps in a new tab (matching the context menu behavior) while keeping existing target-link/app-name routing. Also switch the default body background to white and add a dark-mode media query to use a dark background color.

src/gui/src/UI/Dashboard/TabApps.js

@@ -365,6 +365,16 @@ const TabApps = {
             }
             const appName = $(this).attr('data-app-name');
             const targetLink = $(this).attr('data-target-link');
+            // Ctrl/Cmd+click opens in a new browser tab, mirroring the
+            // context menu's "Open in new tab" item.
+            if ( e.ctrlKey || e.metaKey ) {
+                if ( targetLink && targetLink !== '' ) {
+                    window.open(targetLink, '_blank', 'noopener,noreferrer');
+                } else if ( appName ) {
+                    window.open(`/app/${encodeURIComponent(appName)}`, '_blank', 'noopener,noreferrer');
+                }
+                return;
+            }
             if ( targetLink && targetLink !== '' ) {
                 window.open(targetLink, '_blank', 'noopener,noreferrer');
             } else if ( appName ) {

src/gui/src/css/style.css

@@ -125,10 +125,16 @@ body {
     background: no-repeat center center fixed;
     background-position: center;
     background-size: cover;
-    background-color: #3d4c74;
+    background-color: #ffffff;
     overflow: hidden;
 }
 
+@media (prefers-color-scheme: dark) {
+    body {
+        background-color: #1e1e1e;
+    }
+}
+
 .embedded-in-3rd-party-website, .embedded-in-popup {
     background: none !important;
     background-color: #ccccccbe !important;