fix: update LOG_TZ type to pass pydantic validation

[yaoice]

Checklist:

Important

Please review the checklist below before submitting your pull request.

• Please open an issue before creating a PR or link to an existing issue
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

Description

Update LOG_TZ type to str so that is can pass pydantic validation.

Fixes #10061

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update, included: Dify Document
• Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement
• Dependency upgrade

Testing Instructions

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A
• Test B

[yaoice]

@bowenliang123 @crazywoola help to reivew it, someone also encounter the same problem as issue description #10061 .

[bowenliang123]

Quite surprised the problem you've encountered. It works well with the master branch code on my local environment. Or let me check again on this.

[bowenliang123]

After double check, the problem was confirmed. Please revert #9595 fully, ensuring astimezone accepts the data in tzinfo type rather than string type (or it fails).

[bowenliang123]

It still puzzles me that somehow the unit tests missed this case while it does includes the DifyCofing instance construction. If any default value violates the pydantic validation, it should fail.