feat(ar): 应收账龄看板 + 逾期预警 overdue 接入（阶段A）

T1 逾期预警（§6 财务 2026-10-20 23:23 口径）：
- alert_rules 支持 rule_type=ar_overdue；阈值/责任人/排除名单全量走 params（代码零业务常量）
- 90 天占比红线 key 保留但默认 null 停用（不回落 0.25）；黄线 15%-25% 保留
- 新增逐户红线「>30 天且 >5 万」+ 聚合红线「150+ 占比环比上升 = 结构恶化」
- assignee 派生：manual → 近 3 个月主业务员（zxt_masterbill emp_id → employee_dict.u_Name，
  缺表时降级同库摘要制单人姓名）→ 部门负责人（渠道 118 / 商务 114 / 直属酒窖 117）；
  两路皆失败 ⇒ 该户不生成、进 skipped[]，禁落空 assignee
- POST /run-ar-overdue（dry_run 默认 true）+ check-all 分支；只 INSERT 同一 message 幂等

T2 账龄看板：
- GET /api/cma/ar-aging/{meta,trend,overview,customers,customers/export}；每条查询带 entity_id
- 三口径分列、caliber=all → 400；缺期 has_data=false 且金额 null（不补 0）
- ArAging.vue：口径后缀/截止期徽标/趋势断点/六档堆叠/逐户可排序导出

单测 21 项全通过（SQLite 夹具，不连生产库）；vite build 通过。
阶段A 零生产写：未 push、未部署、未 --apply、未 dry_run=false。

backend/app/main.py

@@ -7,7 +7,7 @@ from fastapi.responses import JSONResponse
 from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
 from dotenv import load_dotenv
 from app.database import init_db, get_db
-from app.api import auth, kpis, kpi_governance, templates, maps, dashboard, data, alerts, ai_analysis, ai_suggestions, alert_rules, users, thresholds, notifications, permissions, action_plans, alignment, org, objectives, versions, budget, cost, predict, reports, security, knowledge, bot_bridge, bot_bridge_v2, bot_suggestions, lead, tenant, customer_dashboard, deviation_push, budget_generate, knowledge_articles, kpi_causality, data_quality, bi_reports, entities, bsc_layers, okr, okr_templates, subjects, driver_budget, bot_kpis, ontology, bot_iron_law, analysis_results, expenses, cash, tax_compliance, verify, growth_quality, products, data_classification, value_sources, zero_based, derivation_rules, cash_classify, cashflow_structure, cash_vouchers_json, ext_input_ledgers, treasury, doc_center, map_completeness, map_summary, map_dimensions
+from app.api import auth, kpis, kpi_governance, templates, maps, dashboard, data, alerts, ai_analysis, ai_suggestions, alert_rules, users, thresholds, notifications, permissions, action_plans, alignment, org, objectives, versions, budget, cost, predict, reports, security, knowledge, bot_bridge, bot_bridge_v2, bot_suggestions, lead, tenant, customer_dashboard, deviation_push, budget_generate, knowledge_articles, kpi_causality, data_quality, bi_reports, entities, bsc_layers, okr, okr_templates, subjects, driver_budget, bot_kpis, ontology, bot_iron_law, analysis_results, expenses, cash, tax_compliance, verify, growth_quality, products, data_classification, value_sources, zero_based, derivation_rules, cash_classify, cashflow_structure, cash_vouchers_json, ext_input_ledgers, treasury, doc_center, map_completeness, map_summary, map_dimensions, ar_aging
 from app.utils.cache import clear_all as clear_cache, delete as delete_cache
 from scripts.erp_sync import run_sync as run_erp_sync
 from app.auth_middleware import require_auth, require_auth_401
@@ -105,6 +105,7 @@ app.include_router(tax_compliance.router)
 app.include_router(verify.router)
 app.include_router(ext_input_ledgers.router)  # 外部输入台账（M2 准入3 派生，2026-09-15）
 app.include_router(treasury.router)  # 司库（资金）阶段一：账户池/头寸/内控闸门（2026-09-15）
+app.include_router(ar_aging.router)  # 应收账龄看板（T2 2026-10-20：逐户·六档·三口径禁合计）
 app.include_router(doc_center.router)  # 文档中心：md 单一来源（运行期读盘，2026-09-24）
 
 @app.exception_handler(Exception)