fix: 工作台KPI级别判断支持反向指标 — 费用率/渠补率/应收天数等'越低越好'指标不再误判green

- my_dashboard的level判断原为actual/target比例法(≥0.9=green)
- 反向指标(费用率24.9%/目标20%)被误判为green，实际应red
- 新增REVERSE_INDICATORS集合：F_COST_RATIO/C_REBATE_RATE/F_AR_DAYS/F_REBATE_RATE/F_FACTORY_REBATE_RATE/F_COST_CONTROL_RATE
- 反向指标逻辑：实际≤目标=绿，≤目标*1.1=黄，否则红

backend/app/api/dashboard.py

@@ -417,6 +417,16 @@ def my_dashboard(
         target = k.target_value
         level = "gray"
         if actual is not None and target:
+            # 反向指标（越低越好）：费用率/渠补率/应收天数/返利率/成本率
+            REVERSE_INDICATORS = {
+                "F_COST_RATIO", "C_REBATE_RATE", "F_AR_DAYS",
+                "F_REBATE_RATE", "F_FACTORY_REBATE_RATE", "F_COST_CONTROL_RATE",
+            }
+            if k.kpi_code in REVERSE_INDICATORS:
+                # 反向：实际≤目标=绿；实际≤目标*1.1=黄；否则红
+                level = "green" if actual <= target else (
+                    "yellow" if actual <= target * 1.1 else "red")
+            else:
                 ratio = actual / target
                 level = "green" if ratio >= 0.9 else ("yellow" if ratio >= 0.7 else "red")