fix(register): handle invalid invite code gracefully

Fix an issue where entering a non-existent invite code during registration would result in an unclear HTTP code 0 error. Now, the system properly validates the invite code and returns a clear error response if the code does not exist.

app/Models/InviteCode.php

@@ -13,4 +13,7 @@ class InviteCode extends Model
         'updated_at' => 'timestamp',
         'status' => 'boolean',
     ];
+
+    const STATUS_UNUSED = 0;
+    const STATUS_USED = 1;
 }