Refactor code and simplify billing services

Code for billing services has been refactored for simplicity and improved organization. This includes updated locations for the 'loadTeamWorkspace' function and adjusted component imports. Redundant scripts have been eliminated and new schemas have been introduced for input data validation.

packages/billing/core/src/schema/create-billing-checkout.schema.ts

@@ -9,4 +9,10 @@ export const CreateBillingCheckoutSchema = z.object({
   trialDays: z.number().optional(),
   customerId: z.string().optional(),
   customerEmail: z.string().email().optional(),
+  variantQuantities: z.array(
+    z.object({
+      variantId: z.string().min(1),
+      quantity: z.number(),
+    }),
+  ),
 });