Add a structured log event for every state transition in markets

[greatest0fallt1me]

Description

This is a backend issue for the GrantFox campaign. Emit structured log events on every market state change for observability and audit pipelines.

Requirements and Context

• LogEvent enum
• Emitted from service layer
• Includes correlation id
• Doc lists events
• Must be secure, tested, and documented
• Should be efficient and easy to review

Suggested Execution

1. Fork the repo and create a branch

   git checkout -b task/market-log-events

2. Implement changes
   • src/services/marketService.ts
   • src/logging/events.ts (new)
   • docs/log-events.md (new)
3. Test and commit
   • Run the repo's standard test suite and lint
   • Cover edge cases; include output in the PR

Example commit message

feat: structured log events for markets

Acceptance Criteria

• Events emitted
• Correlation id present
• Doc shipped
• Tests cover

Guidelines

• Minimum 90% test coverage on changed lines
• Input validation at the boundary; standardized error envelope
• Structured logging with correlation IDs
• Clear documentation and inline comments
• Timeframe: 96 hours