refactor: update WHMCS phone country code handling and schema validation

- Modify the phoneCountryCode assignment in the WHMCS mapper to ensure it is always a string when present.
- Change the phonecc type in the WHMCS raw types schema to use numberLike for improved type safety and validation consistency.

packages/domain/customer/providers/whmcs/mapper.ts

@@ -56,7 +56,7 @@ function normalizeAddress(client: WhmcsRawClient): Address | undefined {
     country: client.country ?? null,
     countryCode: client.countrycode ?? null,
     phoneNumber: client.phonenumberformatted ?? client.phonenumber ?? null,
-    phoneCountryCode: client.phonecc ?? null,
+    phoneCountryCode: client.phonecc == null ? null : String(client.phonecc),
   });
 
   const hasValues = Object.values(address).some(v => v !== undefined && v !== null && v !== "");

packages/domain/customer/providers/whmcs/raw.types.ts

@@ -119,7 +119,7 @@ export const whmcsClientSchema = z
     postcode: z.string().optional(),
     country: z.string().optional(),
     countrycode: z.string().optional(),
-    phonecc: z.string().optional(),
+    phonecc: numberLike.optional(),
     phonenumber: z.string().optional(),
     phonenumberformatted: z.string().optional(),
     telephoneNumber: z.string().optional(),