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/app/models/__init__.py

@@ -17,16 +17,19 @@ from app.models.customer import Customer, OwnershipChangeLog
 from app.models.login_log import LoginLog
 from app.models.operation_log import OperationLog
 from app.models.param import ParamChangeBatch, ParamDefinition, ParamValue
+from app.models.performance_ledger import PerformanceLedger
 from app.models.personnel import Personnel, PersonnelPlan, PersonnelRegion
 from app.models.product import Product
 from app.models.rating import CustomerRatingGrade
 from app.models.receipt import Receipt
 from app.models.role import Permission, Role, RolePermission
+from app.models.settlement import AdjustmentOrder, MonthlySettlement, SettlementItem
 from app.models.shipment import Shipment, ShipmentItem
 from app.models.system_setting import SystemSetting
 from app.models.user import User, UserRole
 
 __all__ = [
+    "AdjustmentOrder",
     "ApprovalOrder",
     "ApprovalStep",
     "Base",
@@ -37,11 +40,13 @@ __all__ = [
     "Customer",
     "CustomerRatingGrade",
     "LoginLog",
+    "MonthlySettlement",
     "OperationLog",
     "OwnershipChangeLog",
     "ParamChangeBatch",
     "ParamDefinition",
     "ParamValue",
+    "PerformanceLedger",
     "Permission",
     "Personnel",
     "PersonnelPlan",
@@ -51,6 +56,7 @@ __all__ = [
     "Role",
     "RolePermission",
     "SecondaryAllocation",
+    "SettlementItem",
     "Shipment",
     "ShipmentItem",
     "SystemSetting",