[Backend] Implement Structured JSON Logging with Log Levels

[devJaja]

Problem

Current logging in backend/src/api/middleware/logger.ts uses plain console.log with a basic timestamp format. This is not machine-parseable, has no log levels, and makes log aggregation (ELK, Datadog, etc.) impossible.

Current State

// logger.ts output format:
// [2024-01-01T00:00:00.000Z] GET /api/tasks 200 45ms

Proposed Solution

1. Add pino as the logging library (fast, structured by default)
2. Create backend/src/logger.ts with configurable levels:
   • LOG_LEVEL env var (debug/info/warn/error)
   • Development: pretty-printed
   • Production: JSON output
3. Create child loggers per module:
   • logger.child({ module: 'coordinator' })
   • logger.child({ module: 'api', correlationId })
4. Replace all console.log/console.error with structured logger
5. Redact sensitive fields (API keys, tokens) automatically

Files to Modify

• backend/src/api/middleware/logger.ts
• backend/src/coordinator/index.ts
• backend/src/db/index.ts
• backend/src/registry/sync.ts
• backend/src/server.ts
• New: backend/src/logger.ts

Acceptance Criteria

• Pino logger configured with JSON output
• LOG_LEVEL env var respected
• All console.log replaced with structured logger
• Correlation IDs included in all log lines
• Sensitive fields redacted in logs
• Pretty-print in development mode
• Performance: no measurable latency increase

Difficulty

High — touches every file that logs

Labels

backend services enhancement

[Bilalishaq7]

Good evening maintener, I can fix this
I would like to take on this task and I will submit a PR shortly

[grantfox-oss]

🦊 GrantFox — @Bilalishaq7 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #110)
2. Your PR will be reviewed by the Epta-Node maintainers

Good luck! Track your progress on GrantFox.