feat: sam_stat 통계 DB 인프라 구축 (Phase 1)

- sam_stat DB 연결 설정 (config/database.php, .env)
- 메타 테이블 마이그레이션 (stat_definitions, stat_job_logs)
- dim_date 차원 테이블 + DimDateSeeder (2020~2030, 4018건)
- 기반 모델: BaseStatModel, StatDefinition, StatJobLog, DimDate
- 집계 커맨드: stat:aggregate-daily, stat:aggregate-monthly
- StatAggregatorService + StatDomainServiceInterface 골격

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

app/Models/Stats/StatJobLog.php

@@ -0,0 +1,53 @@
+<?php
+
+namespace App\Models\Stats;
+
+class StatJobLog extends BaseStatModel
+{
+    protected $table = 'stat_job_logs';
+
+    public $timestamps = false;
+
+    protected $casts = [
+        'target_date' => 'date',
+        'started_at' => 'datetime',
+        'completed_at' => 'datetime',
+        'created_at' => 'datetime',
+    ];
+
+    public function markRunning(): void
+    {
+        $this->update([
+            'status' => 'running',
+            'started_at' => now(),
+        ]);
+    }
+
+    public function markCompleted(int $recordsProcessed = 0): void
+    {
+        $durationMs = $this->started_at
+            ? (int) now()->diffInMilliseconds($this->started_at)
+            : null;
+
+        $this->update([
+            'status' => 'completed',
+            'records_processed' => $recordsProcessed,
+            'completed_at' => now(),
+            'duration_ms' => $durationMs,
+        ]);
+    }
+
+    public function markFailed(string $errorMessage): void
+    {
+        $durationMs = $this->started_at
+            ? (int) now()->diffInMilliseconds($this->started_at)
+            : null;
+
+        $this->update([
+            'status' => 'failed',
+            'error_message' => $errorMessage,
+            'completed_at' => now(),
+            'duration_ms' => $durationMs,
+        ]);
+    }
+}