fix: fix dify-plugin-daemon is pid 1

[fatelei]

Description

Please provide a brief description of the changes made in this pull request.
Please also include the issue number if this is related to an issue using the format Fixes #123 or Closes #123.

Type of Change

• Bug fix
• New feature
• Refactor
• Performance improvement
• Other

Essential Checklist

Testing

• I have tested the changes locally and confirmed they work as expected
• I have added unit tests where necessary and they pass successfully

Bug Fix (if applicable)

• I have used GitHub syntax to close the related issue (e.g., Fixes #123 or Closes #123)

Additional Information

Please provide any additional context that would help reviewers understand the changes.

[gemini-code-assist]

Code Review

This pull request introduces tini as the entrypoint in the local Dockerfile to prevent the Python plugin SDK from incorrectly identifying itself as orphaned when running as PID 1. Feedback suggests adding the -g flag to the tini entrypoint to ensure termination signals are properly forwarded to subprocess groups, facilitating graceful shutdowns.