fix(auth): revert store_id to uuid.UUID in user schemas

CTO review feedback: store_id must remain uuid.UUID since Store
model still uses UUIDPrimaryKeyMixin. Only user_id changes to str.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

common/src/cartsnitch_common/schemas/user.py

@@ -26,7 +26,7 @@ class UserRead(BaseModel):
 
 class UserStoreAccountCreate(BaseModel):
     user_id: str
-    store_id: str
+    store_id: uuid.UUID
     session_data: dict | None = None
     status: AccountStatus = AccountStatus.ACTIVE
 
@@ -36,7 +36,7 @@ class UserStoreAccountRead(BaseModel):
 
     id: uuid.UUID
     user_id: str
-    store_id: str
+    store_id: uuid.UUID
     status: AccountStatus
     session_expires_at: datetime | None
     last_sync_at: datetime | None