fix(bep-caliber): expense and profit sums use net (debit minus credit) under carry_forward=0

ASK-20261002-06 fix04u: admin(5602%) and depreciation(560213) take net amount in both the dashboard card helper and the BEP deriver; sales (5001) keeps credit_amount. Verbatim per proposal section 2. No DB writes, no kpi_values backfill.

backend/scripts/kpi_bep_deriver.py

@@ -9,8 +9,8 @@
 
 口径（与财务Bot报告一致）：
 - 销售收入: voucher_details.subject_code='5001'(主营业务收入) 贷方合计，当年1月至目标月 YTD 月均
-- 管理费:   subject_code LIKE '5602%'(管理费用，含560213折旧) 借方合计，YTD 月均 → 账面口径
-- 折旧:     subject_code = '560213'(管理费用-折旧叶子) 借方合计，YTD 月均 → 现金口径剔除项(eq精确匹配,防5602130误含)
+- 管理费:   subject_code LIKE '5602%'(管理费用，含560213折旧) 借−贷净额合计(carry_forward=0)，YTD 月均 → 账面口径
+- 折旧:     subject_code = '560213'(管理费用-折旧叶子) 借−贷净额合计(carry_forward=0)，YTD 月均 → 现金口径剔除项(eq精确匹配,防5602130误含)
 - 渠补率:   厂家政策定死 84.61% (571103渠补支出/5001销售, 1-7月累计凭证验证≈84.0%~84.6%)
 - 边际贡献率 = 1 - 渠补率 = 15.39%
 - 目标月:   --period 显式指定；默认自动选最近「已结账」完整月（当月跳过）。
@@ -137,8 +137,15 @@ def _month_range(period: str):
 
 def _sum_field(db, entity_id: int, period_from: str, period_to: str,
                field: str, subject_filter=None) -> float:
-    """聚合 voucher_details 金额（元）。subject_filter: ('eq', code) / ('like', prefix)"""
-    q = db.query(func.sum(getattr(VoucherDetail, field))).filter(
+    """聚合 voucher_details 金额（元）。subject_filter: ('eq', code) / ('like', prefix)
+
+    field="net" = 借−贷 净额（口径4：费用/损益一律净额）。
+    ⚠️ 净额只在 carry_forward==0 行域成立（含结转腿时损益类净额恒 0）
+       —— 见 /srv/hermes/wisdom/_decisions/cma-expense-profit-net-caliber-20261002.md。
+    """
+    expr = (VoucherDetail.debit_amount - VoucherDetail.credit_amount
+            if field == "net" else getattr(VoucherDetail, field))
+    q = db.query(func.sum(expr)).filter(
         VoucherDetail.entity_id == entity_id,
         VoucherDetail.carry_forward == 0,
         VoucherDetail.period >= period_from,
@@ -299,9 +306,9 @@ def run_derive(db, entity_id: int, period: str, rebate_rate_pct: float,
 
     # 1. 取数（元 → 万元）
     sales_sum_w = _sum_field(db, entity_id, period_from, period_to, "credit_amount", ("eq", SALES_CODE)) / 10000.0
-    admin_sum_w = _sum_field(db, entity_id, period_from, period_to, "debit_amount", ("like", ADMIN_PREFIX)) / 10000.0
-    rebate_sum_w = _sum_field(db, entity_id, period_from, period_to, "debit_amount", ("eq", REBATE_CODE)) / 10000.0
-    dep_sum_w = _sum_field(db, entity_id, period_from, period_to, "debit_amount", ("eq", DEP_SUBJECT)) / 10000.0
+    admin_sum_w = _sum_field(db, entity_id, period_from, period_to, "net", ("like", ADMIN_PREFIX)) / 10000.0
+    rebate_sum_w = _sum_field(db, entity_id, period_from, period_to, "net", ("eq", REBATE_CODE)) / 10000.0
+    dep_sum_w = _sum_field(db, entity_id, period_from, period_to, "net", ("eq", DEP_SUBJECT)) / 10000.0
 
     sales_avg = sales_sum_w / months
     admin_avg = admin_sum_w / months