Remove billing and checkout redirect buttons and related services

Deleted the billing-redirect-button, checkout-redirect-button, and embedded-stripe-checkout components. Additionally, removed the shadcn directory, which encompassed billing-related icons. This change streamlines the subscription settings interface and organizes the system's payment management. This update is a stepping stone towards improving the billing system's overall architecture.

packages/billing/src/index.ts

@@ -1,2 +1,3 @@
 export * from './create-billing-schema';
 export * from './services/billing-strategy-provider.service';
+export * from './services/billing-webhook-handler.service';