refactor: replace hardcoded hex values with Tailwind semantic tokens

3,200+ hardcoded color values replaced with CSS variable-backed
Tailwind classes (bg-card, text-foreground, border-border, etc.).
Enables light mode via CSS variable swap. Only syntax highlighting
colors and intentional one-offs remain hardcoded (~15 values).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/admin/ActionMenu.tsx

@@ -53,8 +53,8 @@ export function ActionMenu({ items }: ActionMenuProps) {
         ref={buttonRef}
         onClick={() => setOpen(!open)}
         className={cn(
-          'rounded-md p-1.5 text-[#848b9b] transition-colors',
-          'hover:bg-accent hover:text-[#e2e5eb]'
+          'rounded-md p-1.5 text-muted-foreground transition-colors',
+          'hover:bg-accent hover:text-foreground'
         )}
       >
         <MoreHorizontal className="h-4 w-4" />
@@ -63,8 +63,8 @@ export function ActionMenu({ items }: ActionMenuProps) {
         <div
           ref={menuRef}
           className={cn(
-            'fixed z-50 min-w-[160px] rounded-md border border-[#1e2130]',
-            'bg-[#14161d] py-1 shadow-lg animate-scale-in'
+            'fixed z-50 min-w-[160px] rounded-md border border-border',
+            'bg-card py-1 shadow-lg animate-scale-in'
           )}
           style={{
             top: `${menuPosition.top}px`,
@@ -81,7 +81,7 @@ export function ActionMenu({ items }: ActionMenuProps) {
                 'disabled:opacity-50 disabled:pointer-events-none',
                 item.destructive
                   ? 'text-red-400 hover:bg-red-400/10'
-                  : 'text-[#848b9b] hover:bg-accent'
+                  : 'text-muted-foreground hover:bg-accent'
               )}
             >
               {item.icon}