fix: resolve icon-16.png asset path warnings in CSS

- Update background image references to use absolute paths (/icon-16.png)
- This fixes Vite build warnings about unresolved asset references
- The icon file exists in static/icon-16.png and needs the leading slash

Author: MrCoder

src/style.css

@@ -751,7 +751,7 @@ body > #demo-frame {
   height: 18px;
   width: 18px;
   margin-right: 5px;
-  background: url(icon-16.png) no-repeat;
+  background: url(/icon-16.png) no-repeat;
   vertical-align: middle;
   -webkit-filter: grayscale(0.9);
   filter: grayscale(0.9);
@@ -764,7 +764,7 @@ body > #demo-frame {
   height: 20px;
   width: 20px;
   margin-right: 0px;
-  background: url(icon-16.png) 0px 0px no-repeat;
+  background: url(/icon-16.png) 0px 0px no-repeat;
   -webkit-filter: grayscale(0);
   filter: grayscale(0);
   opacity: 1;