[CLEAN] Synthetic Benchmark PR #30170 - feat(refactoring): Support Structured Logging (JSON)

[bar-qodo]

Benchmark PR langgenius#30170

Type: Clean (correct implementation)

Original PR Title: feat(refactoring): Support Structured Logging (JSON)
Original PR Description: > [!IMPORTANT]

1. Make sure you have read our contribution guidelines
2. Ensure there is an associated issue and you have been assigned to it
3. Use the correct syntax to link this PR: Fixes #<issue number>.

Fixes langgenius#30169

Summary

What

This PR introduces structured logging support (JSON format) to the backend service. It standardizes log outputs, making them machine-readable and consistent.

Why

To better integrate with modern log aggregation and observability systems (e.g., ELK, Datadog, Loki). Structured logging eliminates the need for complex regex parsing and improves query capabilities on log fields.

Key Changes

• Refactored logging implementation to support JSON serialization.
• Unified log field naming (e.g., level, msg, ts, trace_id).
• Added configuration to toggle between console (text) and json formats (defaulting to text for dev environments).

Fixes langgenius#30169

Screenshots

Before	After

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

Original PR URL: langgenius#30170