feat: sam_stat P1 도메인 확장 (Phase 3)

- 차원 테이블: dim_client, dim_product 마이그레이션 + SCD Type 2 동기화 (DimensionSyncService)
- 재고 통계: stat_inventory_daily + InventoryStatService (stocks, stock_transactions, inspections)
- 견적/영업 통계: stat_quote_pipeline_daily + QuoteStatService (quotes, biddings, sales_prospects)
- 인사/근태 통계: stat_hr_attendance_daily + HrStatService (attendances, leaves, user_tenants)
- KPI/알림: stat_kpi_targets, stat_alerts + KpiAlertService + StatCheckKpiAlertsCommand
- StatAggregatorService에 inventory, quote, hr 도메인 추가 (총 6개 도메인)
- 스케줄러: stat:check-kpi-alerts 매일 09:00 등록

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/Models/Stats/StatKpiTarget.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace App\Models\Stats;
+
+class StatKpiTarget extends BaseStatModel
+{
+    protected $table = 'stat_kpi_targets';
+
+    protected $casts = [
+        'target_value' => 'decimal:2',
+    ];
+}