Trade State Machine & Audit Logging

[NengakDakup]

Description:
Implement and persist trade state transitions (initiated, matched, payout pending, payout complete, released, failed, etc.) with audit logs.

Acceptance Criteria:

• State machine logic for all trade transitions
• Store audit logs for each state change and action
• Expose trade status via API

Subtasks:

• State machine implementation
• Audit log schema and storage
• Trade status API