feat(计费): 支持账号计费倍率快照与统计展示

- 新增 accounts.rate_multiplier（默认 1.0，允许 0）
- 使用 usage_logs.account_rate_multiplier 记录倍率快照，避免历史回算
- 统计/导出/管理端展示账号口径费用（total_cost * account_rate_multiplier）

backend/ent/usagelog_update.go

@@ -415,6 +415,33 @@ func (_u *UsageLogUpdate) AddRateMultiplier(v float64) *UsageLogUpdate {
 	return _u
 }
 
+// SetAccountRateMultiplier sets the "account_rate_multiplier" field.
+func (_u *UsageLogUpdate) SetAccountRateMultiplier(v float64) *UsageLogUpdate {
+	_u.mutation.ResetAccountRateMultiplier()
+	_u.mutation.SetAccountRateMultiplier(v)
+	return _u
+}
+
+// SetNillableAccountRateMultiplier sets the "account_rate_multiplier" field if the given value is not nil.
+func (_u *UsageLogUpdate) SetNillableAccountRateMultiplier(v *float64) *UsageLogUpdate {
+	if v != nil {
+		_u.SetAccountRateMultiplier(*v)
+	}
+	return _u
+}
+
+// AddAccountRateMultiplier adds value to the "account_rate_multiplier" field.
+func (_u *UsageLogUpdate) AddAccountRateMultiplier(v float64) *UsageLogUpdate {
+	_u.mutation.AddAccountRateMultiplier(v)
+	return _u
+}
+
+// ClearAccountRateMultiplier clears the value of the "account_rate_multiplier" field.
+func (_u *UsageLogUpdate) ClearAccountRateMultiplier() *UsageLogUpdate {
+	_u.mutation.ClearAccountRateMultiplier()
+	return _u
+}
+
 // SetBillingType sets the "billing_type" field.
 func (_u *UsageLogUpdate) SetBillingType(v int8) *UsageLogUpdate {
 	_u.mutation.ResetBillingType()
@@ -807,6 +834,15 @@ func (_u *UsageLogUpdate) sqlSave(ctx context.Context) (_node int, err error) {
 	if value, ok := _u.mutation.AddedRateMultiplier(); ok {
 		_spec.AddField(usagelog.FieldRateMultiplier, field.TypeFloat64, value)
 	}
+	if value, ok := _u.mutation.AccountRateMultiplier(); ok {
+		_spec.SetField(usagelog.FieldAccountRateMultiplier, field.TypeFloat64, value)
+	}
+	if value, ok := _u.mutation.AddedAccountRateMultiplier(); ok {
+		_spec.AddField(usagelog.FieldAccountRateMultiplier, field.TypeFloat64, value)
+	}
+	if _u.mutation.AccountRateMultiplierCleared() {
+		_spec.ClearField(usagelog.FieldAccountRateMultiplier, field.TypeFloat64)
+	}
 	if value, ok := _u.mutation.BillingType(); ok {
 		_spec.SetField(usagelog.FieldBillingType, field.TypeInt8, value)
 	}
@@ -1406,6 +1442,33 @@ func (_u *UsageLogUpdateOne) AddRateMultiplier(v float64) *UsageLogUpdateOne {
 	return _u
 }
 
+// SetAccountRateMultiplier sets the "account_rate_multiplier" field.
+func (_u *UsageLogUpdateOne) SetAccountRateMultiplier(v float64) *UsageLogUpdateOne {
+	_u.mutation.ResetAccountRateMultiplier()
+	_u.mutation.SetAccountRateMultiplier(v)
+	return _u
+}
+
+// SetNillableAccountRateMultiplier sets the "account_rate_multiplier" field if the given value is not nil.
+func (_u *UsageLogUpdateOne) SetNillableAccountRateMultiplier(v *float64) *UsageLogUpdateOne {
+	if v != nil {
+		_u.SetAccountRateMultiplier(*v)
+	}
+	return _u
+}
+
+// AddAccountRateMultiplier adds value to the "account_rate_multiplier" field.
+func (_u *UsageLogUpdateOne) AddAccountRateMultiplier(v float64) *UsageLogUpdateOne {
+	_u.mutation.AddAccountRateMultiplier(v)
+	return _u
+}
+
+// ClearAccountRateMultiplier clears the value of the "account_rate_multiplier" field.
+func (_u *UsageLogUpdateOne) ClearAccountRateMultiplier() *UsageLogUpdateOne {
+	_u.mutation.ClearAccountRateMultiplier()
+	return _u
+}
+
 // SetBillingType sets the "billing_type" field.
 func (_u *UsageLogUpdateOne) SetBillingType(v int8) *UsageLogUpdateOne {
 	_u.mutation.ResetBillingType()
@@ -1828,6 +1891,15 @@ func (_u *UsageLogUpdateOne) sqlSave(ctx context.Context) (_node *UsageLog, err
 	if value, ok := _u.mutation.AddedRateMultiplier(); ok {
 		_spec.AddField(usagelog.FieldRateMultiplier, field.TypeFloat64, value)
 	}
+	if value, ok := _u.mutation.AccountRateMultiplier(); ok {
+		_spec.SetField(usagelog.FieldAccountRateMultiplier, field.TypeFloat64, value)
+	}
+	if value, ok := _u.mutation.AddedAccountRateMultiplier(); ok {
+		_spec.AddField(usagelog.FieldAccountRateMultiplier, field.TypeFloat64, value)
+	}
+	if _u.mutation.AccountRateMultiplierCleared() {
+		_spec.ClearField(usagelog.FieldAccountRateMultiplier, field.TypeFloat64)
+	}
 	if value, ok := _u.mutation.BillingType(); ok {
 		_spec.SetField(usagelog.FieldBillingType, field.TypeInt8, value)
 	}