Bug: Email action token not enforced or invalidated, allowing multiple actions on the same event

Preconditions:
An event exists with status pending review.

Steps to Reproduce:

1. Trigger a status update email for an event (e.g., “Approve” / “Reject”).
2. Open the email and click the provided action link.
3. The event status is updated successfully.
4. Reuse the same link or a different link from the same email.
5. Observe the behavior.

Expected Result:
The email token is validated and tied to a single action.
Once an action is performed, the token becomes expired/invalid and cannot be reused.
A second attempt with the same token should return an error (e.g., “Token expired or invalid”).
The system should prevent conflicting actions (e.g., approving and then rejecting with the same token).

Actual Result:
The same token can be reused multiple times.
Different actions (approve and reject) can be performed using the same token.
The token is not considered in validation logic after the first use.

'Acceptance Criteria:
Token is strictly validated against the requested action.
After a successful action, the token is invalidated and cannot be reused.
Attempting a second use returns an error message and no status change occurs.
Conflicting actions cannot be performed with the same token.

https://github.com/user-attachments/assets/0aa2a6ab-12e7-4b86-bfc3-53990fc2f93f

Issue には、ソースファイル、テスト、エントリポイントが特定されていません。まずメールのアクショントークンハンドラーとその検証パスを見つけます。完了条件は、アクションが要求されたトークンとアクションに紐付けられ、使用に成功するとトークンが無効化され、再利用時にはステータスを変更せずにエラーが返されることです。