fix(colors): Replace hardcoded black with background color token (#5815)

* Update all black to background

* remove --canvas token, keep intentional bg-black

* Move bg-black from grid container to individual viewport panes

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Co-authored-by: Alireza <ar.sedghi@gmail.com>

extensions/usAnnotation/src/panels/USAnnotationPanel.tsx

@@ -395,7 +395,7 @@ export default function USAnnotationPanel() {
    *  🖼  Final Render                                      */
   return (
     <div
-      className="text-foreground h-full bg-black"
+      className="text-foreground h-full bg-background"
       style={{ minWidth: 240, maxWidth: 480, width: '100%' }}
     >
       {/* Workflow */}