오늘 이슈(TodayIssue) 기능 구현

- TodayIssue 모델 및 마이그레이션 추가
- TodayIssueController, TodayIssueService 구현
- TodayIssueObserverService 및 Observer 패턴 적용
- DailyReportService 연동
- Swagger API 문서 업데이트
- 라우트 추가

app/Observers/TodayIssue/ApprovalStepIssueObserver.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace App\Observers\TodayIssue;
+
+use App\Models\Tenants\ApprovalStep;
+use App\Services\TodayIssueObserverService;
+use Illuminate\Support\Facades\Log;
+
+/**
+ * ApprovalStep 모델의 TodayIssue Observer
+ */
+class ApprovalStepIssueObserver
+{
+    public function __construct(
+        protected TodayIssueObserverService $service
+    ) {}
+
+    public function created(ApprovalStep $step): void
+    {
+        $this->safeExecute(fn () => $this->service->handleApprovalStepChange($step));
+    }
+
+    public function updated(ApprovalStep $step): void
+    {
+        $this->safeExecute(fn () => $this->service->handleApprovalStepChange($step));
+    }
+
+    public function deleted(ApprovalStep $step): void
+    {
+        $this->safeExecute(fn () => $this->service->handleApprovalStepDeleted($step));
+    }
+
+    protected function safeExecute(callable $callback): void
+    {
+        try {
+            $callback();
+        } catch (\Throwable $e) {
+            Log::warning('TodayIssue ApprovalStepObserver failed', [
+                'error' => $e->getMessage(),
+            ]);
+        }
+    }
+}