feat: [calendar,vat] 캘린더 CRUD 및 부가세 상세 조회 API 추가

- CalendarController/Service: 일정 등록/수정/삭제 API 추가
- VatController/Service: getDetail() 상세 조회 (요약, 참조테이블, 미발행 목록, 신고기간 옵션)
- 라우트: POST/PUT/DELETE /calendar/schedules, GET /vat/detail 추가

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Services/CalendarService.php

@@ -226,6 +226,78 @@ private function getLeaveSchedules(
         });
     }
 
+    /**
+     * 일정 등록
+     */
+    public function createSchedule(array $data): array
+    {
+        $schedule = Schedule::create([
+            'tenant_id' => $this->tenantId(),
+            'title' => $data['title'],
+            'description' => $data['description'] ?? null,
+            'start_date' => $data['start_date'],
+            'end_date' => $data['end_date'],
+            'start_time' => $data['start_time'] ?? null,
+            'end_time' => $data['end_time'] ?? null,
+            'is_all_day' => $data['is_all_day'] ?? true,
+            'type' => Schedule::TYPE_EVENT,
+            'color' => $data['color'] ?? null,
+            'is_active' => true,
+            'created_by' => $this->apiUserId(),
+        ]);
+
+        return [
+            'id' => $schedule->id,
+            'title' => $schedule->title,
+            'start_date' => $schedule->start_date?->format('Y-m-d'),
+            'end_date' => $schedule->end_date?->format('Y-m-d'),
+        ];
+    }
+
+    /**
+     * 일정 수정
+     */
+    public function updateSchedule(int $id, array $data): array
+    {
+        $schedule = Schedule::where('tenant_id', $this->tenantId())
+            ->findOrFail($id);
+
+        $schedule->update([
+            'title' => $data['title'],
+            'description' => $data['description'] ?? null,
+            'start_date' => $data['start_date'],
+            'end_date' => $data['end_date'],
+            'start_time' => $data['start_time'] ?? null,
+            'end_time' => $data['end_time'] ?? null,
+            'is_all_day' => $data['is_all_day'] ?? true,
+            'color' => $data['color'] ?? null,
+            'updated_by' => $this->apiUserId(),
+        ]);
+
+        return [
+            'id' => $schedule->id,
+            'title' => $schedule->title,
+            'start_date' => $schedule->start_date?->format('Y-m-d'),
+            'end_date' => $schedule->end_date?->format('Y-m-d'),
+        ];
+    }
+
+    /**
+     * 일정 삭제 (소프트 삭제)
+     */
+    public function deleteSchedule(int $id): array
+    {
+        $schedule = Schedule::where('tenant_id', $this->tenantId())
+            ->findOrFail($id);
+
+        $schedule->update(['deleted_by' => $this->apiUserId()]);
+        $schedule->delete();
+
+        return [
+            'id' => $schedule->id,
+        ];
+    }
+
     /**
      * 범용 일정 조회 (본사 공통 + 테넌트 일정)
      */