[GATEWAY] 12:00:00 trace=1a2b → POST /api/payments  
[AUTH] 12:00:00 trace=1a2b → Token OK (12ms)  
[BILLING] 12:00:01 trace=1a2b → Sent charge request → OK (310ms)  
[WEBHOOK] 12:00:03 trace=1a2b → ERROR: signature mismatch  
[PAYMENTS] 12:00:03 trace=1a2b → Payment marked failed  
[EMAIL] 12:00:04 trace=1a2b → Notification: “Payment declined”