fix(fetch-caliber): 取数层排除半年/预测伪期间 + subjects 响应补 entity_id

R3 期间口径（仅 YYYY-MM）延伸到取数层：新增 alert_entity_scope.month_period_clause()（跨库可移植 SQL 等价式），应用到 15 个文件 26 处「按 period 倒序取最新值/最近N期」位点；dashboard 原 MySQL-only REGEXP 正则收口到同单一事实源。

GET /api/cma/subjects 响应增补 entity_id（NULL=全局标准准则科目 / N=账套私有明细），既有 10 字段语义与名称不变。

证据：pending-tasks/_reports/yanxue-20260924-cma-fetch-caliber-fixes-fullstack.md（改前/改后 A/B：F_NET_PROFIT 2026-H2/-55.0 → 2026-08/-10.46）。新增 7 例回归测试；全量 1 failed(预存在) 1473 passed，基线同项。

backend/app/api/reports.py

@@ -20,6 +20,7 @@ from app.database import get_db
 from app.auth_middleware import require_role, require_auth
 from app.models import KPIDefinition, KPIValue, BudgetPlan, StrategicMap, KPIAlert, User, Subject, ActionPlan, OperationLog, ReportHistory
 from app.utils.deviation_engine import calc_period_deviation, calc_period_diff, calc_deviation, get_budget_for_kpi
+from app.utils.alert_entity_scope import month_period_clause
 from app.utils.voucher_guard import apply_voucher_guard
 from app.services import report_reclass
 from app.deps import get_entity_id, assert_entity_slug_scope, resolve_session_slug
@@ -243,7 +244,8 @@ def get_kpi_trends(
     results = []
     for kpi in kpis:
         values = db.query(KPIValue).filter(
-            KPIValue.kpi_id == kpi.id
+            KPIValue.kpi_id == kpi.id,
+            month_period_clause(KPIValue.period),
         ).order_by(KPIValue.period.desc()).limit(months).all()
         values.reverse()
 
@@ -2387,6 +2389,7 @@ def _fetch_kpi_data(db: Session, entity_id: int = 1) -> list:
         latest = db.query(KPIValue).filter(
             KPIValue.kpi_id == k.id,
             KPIValue.actual_value.isnot(None),
+            month_period_clause(KPIValue.period),
         ).order_by(KPIValue.period.desc()).first()
 
         alerts = db.query(KPIAlert).filter(