Improve CSS performance and add fallback values

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

examples/crm-app/src/index.css

@@ -64,13 +64,13 @@
     --ring: 212.7 26.8% 83.9%;
   }
 
-  * {
+  *[class*="border"] {
     border-color: hsl(var(--border));
   }
 
   body {
-    background-color: hsl(var(--background));
-    color: hsl(var(--foreground));
+    background-color: hsl(var(--background, 0 0% 100%));
+    color: hsl(var(--foreground, 222.2 84% 4.9%));
   }
 }