refactor: Organize mail, stripe, gift, and Claude authentication modules into a new core package and update imports.

core/models.py

@@ -0,0 +1,10 @@
+import uuid
+
+
+class ClaudeAccount:
+    def __init__(self, email, session_key, org_uuid, user_agent):
+        self.email = email
+        self.session_key = session_key
+        self.org_uuid = org_uuid
+        self.user_agent = user_agent
+        self.device_id = str(uuid.uuid4())