feat(usage): add reasoning effort column

backend/internal/handler/dto/mappers.go

@@ -366,6 +366,7 @@ func usageLogFromServiceUser(l *service.UsageLog) UsageLog {
 		AccountID:             l.AccountID,
 		RequestID:             l.RequestID,
 		Model:                 l.Model,
+		ReasoningEffort:       l.ReasoningEffort,
 		GroupID:               l.GroupID,
 		SubscriptionID:        l.SubscriptionID,
 		InputTokens:           l.InputTokens,

backend/internal/handler/dto/types.go

@@ -222,6 +222,9 @@ type UsageLog struct {
 	AccountID int64  `json:"account_id"`
 	RequestID string `json:"request_id"`
 	Model     string `json:"model"`
+	// ReasoningEffort is the request's reasoning effort level (OpenAI Responses API).
+	// nil means not provided / not applicable.
+	ReasoningEffort *string `json:"reasoning_effort,omitempty"`
 
 	GroupID        *int64 `json:"group_id"`
 	SubscriptionID *int64 `json:"subscription_id"`