feat: initial commit — asaas-checkout template white-label

Template genérico de checkout com ASAAS, parametrizado via env vars.
Inclui fluxo completo: checkout → pedido → polling → webhook → admin.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/dashboard-shell.tsx

@@ -0,0 +1,12 @@
+import { cn } from "@/lib/utils"
+import type React from "react"
+
+interface DashboardShellProps extends React.HTMLAttributes<HTMLDivElement> {}
+
+export function DashboardShell({ children, className, ...props }: DashboardShellProps) {
+  return (
+    <div className={cn("container space-y-8 py-8", className)} {...props}>
+      {children}
+    </div>
+  )
+}