feat(visual-edits): aplica visual neon azul no botão Visual Edits (#83)

Mantém tamanho (h-6, px-2, text-[11px]) e ícone (MousePointerClick h-3.5 w-3.5)
do botão no painel de preview, adicionando:
- borda arredondada (rounded-full) com cor azul translúcida
- linhas neon gradiente no topo (hover) e na base (sutil)
- estado ativo em azul sólido

Co-authored-by: Claude <noreply@anthropic.com>

Author: vilpessoa

src/components/ViewportToolbar.tsx

@@ -35,14 +35,16 @@ export function ViewportToolbar({
         onClick={onToggleVisualEdits}
         aria-pressed={visualEditsEnabled}
         className={cn(
-          'inline-flex h-6 items-center gap-1.5 rounded-md px-2 text-[11px] font-medium transition-colors',
+          'relative group inline-flex h-6 items-center gap-1.5 rounded-full border px-2 text-[11px] font-medium text-center transition-all duration-200',
           visualEditsEnabled
-            ? 'bg-primary/15 text-primary'
-            : 'text-muted-foreground hover:bg-accent hover:text-foreground',
+            ? 'bg-blue-500 hover:bg-blue-600 text-white border-transparent hover:border-foreground/50'
+            : 'bg-blue-500/5 hover:bg-blue-500/0 border-blue-500/20 text-foreground',
         )}
       >
+        <span className="pointer-events-none absolute inset-x-0 inset-y-0 mx-auto block h-px w-3/4 bg-gradient-to-r from-transparent via-blue-600 to-transparent opacity-0 transition-all duration-500 ease-in-out group-hover:opacity-100 dark:via-blue-500" />
         <MousePointerClick className="h-3.5 w-3.5" />
         <span className="hidden sm:inline">Visual Edits</span>
+        <span className="pointer-events-none absolute inset-x-0 -bottom-px mx-auto block h-px w-3/4 bg-gradient-to-r from-transparent via-blue-600 to-transparent transition-all duration-500 ease-in-out group-hover:opacity-30 dark:via-blue-500" />
       </button>
     </div>
   );