#776 CRITICAL: approval_service.py missing workflow_run_id on emit_event

ApprovalService.approve() and reject() methods emit events without passing workflow_run_id. Since migration 01KDX91GQGF3KDVG3EZWDWKRFT enforces workflow_run_id is required, this will cause ValueError at runtime. Location: engine/services/approval_service.py:166-170 and 229-233. Fix: Add workflow_run_id=uuid.UUID(workflow_run_id) to emit_event calls.