fix: Fix long message response error

[noahc1510]

Description

When I chat with a large database, the LLM will response a large content. The pymysql will feedback this error message: Data too long for column 'message_detail' at row 1.
This PR change the type of message_detail from text to longtext.

How Has This Been Tested?

Reproduct that case I wrote before, the bug has been fix.

Snapshots:

Checklist:

• My code follows the style guidelines of this project
• I have already rebased the commits and make the commit message conform to the project standard.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• Any dependent changes have been merged and published in downstream modules

[csunny]

@noahc1510 thank you for your contribution, it's useful.

[yhjun1026]

r+