feat(logger): add HTTP request/response logging fields

[AdaAibaby]

Summary

Add structured HTTP request/response logging fields to the logger package.

This PR introduces reusable zap logger fields for standard HTTP metadata:

• Request ID tracing (X-Request-ID, X-Trace-ID, X-Correlation-ID)
• HTTP version
• Request/response body size
• API operation (method + path)
• Remote client IP with proxy header support
• Cache status
• Structured API error object
• HTTP status code to error code mapping

All functions are fully covered by unit tests.

Changes

• Added request_fields.go – HTTP logging field functions
• Added request_fields_test.go – comprehensive test suite

Testing

• All unit tests pass
• Coverage: 32.6%
• Verified cross-environment stability

[claude]

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[jakubno]

@AdaAibaby could you add motivation for this? I don't see the methods used anywhere

[AdaAibaby]

@AdaAibaby could you add motivation for this? I don't see the methods used anywhere

@jakubno Thanks for the feedback! You're right that these methods aren't used yet in the current codebase.

Motivation and Context:
This stems from debugging a 502 error in the dashboard. After investigation, the issue was traced to the LB returning a static page (see GitHub issue #1262), but I noticed that when the dashboard returns a 502, the API responses lacked clear, structured logging for request metadata. This made it hard to diagnose distributed tracing, client IPs, request sizes, and error codes in production logs.

These functions (WithRequestID, WithRemoteIP, WithAPIError, etc.) provide standardized Zap logging fields for HTTP requests, enabling structured logging of key metadata (e.g., request IDs from headers like X-Request-ID/X-Trace-ID, real client IPs from X-Forwarded-For, API operations, and error codes). They follow Zap best practices and prepare the codebase for better observability, making future debugging of issues like 502s much easier by ensuring consistent, searchable logs.

While not integrated yet, they're designed for use in HTTP middleware or handlers (e.g., in packages/dashboard-api/internal/handlers/). For example, we could add them to request logging like:

logger.Info("Request processed", 
    request_fields.WithRequestID(r),
    request_fields.WithRemoteIP(r),
    request_fields.WithAPIError("INTERNAL_ERROR", "upstream failure"),
)