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/app/api/dashboard.py

@@ -27,8 +27,8 @@ router = APIRouter(prefix="/api/cma/dashboard", tags=["驾驶舱"],
 # ── 本量利·保本点 卡片只读数据（cma-bep-kpi Phase2 2026-09-08）──
 # 口径与 backend/scripts/kpi_bep_deriver.py 完全一致：
 #  月销 = voucher_details subject 5001(主营业务收入) 贷方 YTD 月均（万元）
-#  月管理费 = 5602% 借方 YTD 月均（账面口径含折旧）
-#  折旧 = 560213 借方 YTD 月均
+#  月管理费 = 5602% 借−贷 净额 YTD 月均（carry_forward=0 行域；账面口径含折旧）
+#  折旧 = 560213 借−贷 净额 YTD 月均（同上；口径4 见 _decisions/cma-expense-profit-net-caliber-20261002.md）
 #  渠补率 = 厂家政策 84.61%（财务Bot权威口径）
 #  保本额 = 月固定成本 ÷ (1-渠补率)
 # 账面口径(含折旧) / 现金口径(剔除折旧) 双口径只读返回，无写操作。
@@ -46,9 +46,14 @@ def _bep_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)
 
+    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。
     作废/撤单标记过滤（2026-09-14 收口）: 已作废凭证不参与 BEP 均值。
     """
-    q = db.query(func.sum(getattr(VoucherDetail, field))).filter(
+    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,
@@ -131,9 +136,9 @@ def get_bep_card(
     sales_avg = _bep_sum_field(db, entity_id, period_from, period_to,
                                "credit_amount", ("eq", BEP_SALES_SUBJECT)) / 10000.0 / months
     admin_avg = _bep_sum_field(db, entity_id, period_from, period_to,
-                               "debit_amount", ("like", BEP_ADMIN_PREFIX)) / 10000.0 / months
+                               "net", ("like", BEP_ADMIN_PREFIX)) / 10000.0 / months
     dep_avg = _bep_sum_field(db, entity_id, period_from, period_to,
-                             "debit_amount", ("eq", BEP_DEP_SUBJECT)) / 10000.0 / months
+                             "net", ("eq", BEP_DEP_SUBJECT)) / 10000.0 / months
     rebate_pct = BEP_REBATE_POLICY_PCT
     cm_pct = 100.0 - rebate_pct