Added the ability to delete all conversation history at once

[lastshogun13]

こちらのIssue #1333にあった過去の会話履歴をまとめて削除する機能を実装しました。

実装方針として、新規のLambda関数を作成せず既存のLambda関数を複数回実行する方式を採用しました。また、頻繁に使う機能ではなく誤操作も避けたいため、設定画面内のボタンとして実装しています。

Description of Changes

This PR adds a "Delete All Conversation History" feature to the Settings page, allowing users to delete all their chat history at once.

Changes include:

• Added deleteAllChats function in useChatApi.ts that paginates through all chats and deletes them using existing API
• Created new DialogConfirmDeleteAllChats component to confirm the deletion action with users
• Updated useChatList.ts hook to support batch deletion with optimistic cache updates
• Fixed a bug in packages/cdk/lambda/repository.ts where message deletion failed when a chat had more than 25 messages (DynamoDB BatchWrite limit)
• Added "Delete All Conversation History" button in Settings page
• Added internationalization support for 6 languages (en, ja, ko, th, vi, zh)

Impact on existing users:

• No breaking changes
• New optional feature accessible from Settings page
• Requires user confirmation before deletion to prevent accidental data loss

Checklist

• Modified relevant documentation
• Verified operation in local environment
• Executed npm run cdk:test and if there are snapshot differences, execute npm run cdk:test:update-snapshot to update snapshots

Related Issues

• 過去の会話履歴をまとめて削除できるようにしたい #1333

[tbrand]

Good change! Thanks!

[tbrand]

LGTM