feat(migration): V7 核算台账/月结/调整单四表与核算纯函数

- V7 四表：performance_ledgers（append-only 版本行，uk(receipt_id,calc_version)
  库级防重兜底）/monthly_settlements（月份 uk，通过即锁定终态）/
  settlement_items（按人固化可负工资，uk 三列）/adjustment_orders（TZ 单号）
- registry +1：approval.adjustment.enabled（19 项，BOOL 首组扩至三开关）
- formula 补核算纯函数：clamp_weight_r（从预览内联提取共用）/monthly_salary
  三口径/probation_annual_note/manager_team_share（#12 暂口径：基数不含
  经理个人户业绩，聚合集中一处答复后只改）
- 迁移 downgrade 只保留 drop_table+alter 回滚+种子行反向 DELETE；
  performance_ledgers 表名复数（test_models 红线断言）
- 断言同步：EXPECTED_TABLES 四新表/registry 19/BOOL 三开关/conftest
  清理四新表与 ParamValue 边界 22
- schema_sync+全量单测 460 passed

Co-Authored-By: Claude Code <noreply@anthropic.com>

backend/tests/unit/test_formula.py

@@ -11,10 +11,14 @@ from fractions import Fraction
 
 from app.services.formula import (
     apply_barter,
+    clamp_weight_r,
     converted_profit,
+    manager_team_share,
+    monthly_salary,
     payment_days,
     payment_weight,
     performance_amount,
+    probation_annual_note,
     profit_rate,
     salesperson_rate,
     start_payment_ok,
@@ -137,3 +141,68 @@ class TestModifiers:
 
     def test_起付判定_未达到60点(self) -> None:
         assert start_payment_ok(Decimal("59999"), Decimal("100000"), Fraction(60)) is False
+
+
+class TestClampWeightR:
+    """R 钳制：向下取整 + [0,100] 封顶封底（从预览内联提取的共用实现）。"""
+
+    def test_向下取整(self) -> None:
+        assert clamp_weight_r(Decimal("5999.99"), Decimal("10000")) == 59
+
+    def test_封顶100_封底0(self) -> None:
+        assert clamp_weight_r(Decimal("20000"), Decimal("10000")) == 100
+        assert clamp_weight_r(Decimal("0"), Decimal("10000")) == 0
+
+    def test_销售额0_防御0(self) -> None:
+        assert clamp_weight_r(Decimal("100"), Decimal("0")) == 0
+
+
+class TestMonthlySalary:
+    """月工资分岗口径三档（对照表 #8）。"""
+
+    def test_INCLUDE_绩效加基本(self) -> None:
+        assert monthly_salary(Decimal("1000"), Decimal("3000"), "INCLUDE") == Decimal("4000")
+
+    def test_DEDUCT_绩效减基本_可为负(self) -> None:
+        assert monthly_salary(Decimal("1000"), Decimal("3000"), "DEDUCT") == Decimal("-2000")
+
+    def test_EXCLUDE_仅绩效(self) -> None:
+        assert monthly_salary(Decimal("1000"), Decimal("3000"), "EXCLUDE") == Decimal("1000")
+
+    def test_基本缺失按0(self) -> None:
+        assert monthly_salary(Decimal("1000"), None, "INCLUDE") == Decimal("1000")
+
+    def test_未知口径报错(self) -> None:
+        import pytest
+
+        with pytest.raises(ValueError):
+            monthly_salary(Decimal("1"), Decimal("1"), "UNKNOWN")
+
+
+class TestProbationAnnualNote:
+    """试用期年累计说明：超阈值才有 note，金额精确到分。"""
+
+    def test_未超阈值_无说明(self) -> None:
+        assert probation_annual_note(Decimal("18000"), Decimal("18000")) is None
+        assert probation_annual_note(Decimal("100"), Decimal("18000")) is None
+
+    def test_超额_给出精确差额(self) -> None:
+        note = probation_annual_note(Decimal("20000.5"), Decimal("18000"))
+        assert note is not None and "2000.50" in note
+
+
+class TestManagerTeamShare:
+    """经理 12.5%+5% 聚合（#12 暂口径：基数不含经理个人户业绩——由调用方
+    传入的基数集合保证，本函数只做乘法与求和）。"""
+
+    def test_两段乘加_精确分数(self) -> None:
+        # 入参为百分数（与种子一致：12.5 表示 12.5%）：10000×12.5%=1250、50000×5%=2500
+        got = manager_team_share(
+            Decimal("10000"), Decimal("50000"), team_pct=Fraction(25, 2), company_pct=Fraction(5)
+        )
+        assert got == Decimal("3750")
+
+    def test_零基数_零结果(self) -> None:
+        assert manager_team_share(
+            Decimal("0"), Decimal("0"), team_pct=Fraction(0), company_pct=Fraction(0)
+        ) == Decimal("0")