feat: I-8 휴가 정책 관리 API 구현

- LeavePolicyController: 휴가 정책 CRUD API
- LeavePolicyService: 정책 관리 로직
- LeavePolicy 모델: 다중 테넌트 지원
- FormRequest 검증 클래스
- Swagger 문서화
- leave_policies 테이블 마이그레이션

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/Services/LeavePolicyService.php

@@ -0,0 +1,70 @@
+<?php
+
+namespace App\Services;
+
+use App\Models\Tenants\LeavePolicy;
+
+class LeavePolicyService extends Service
+{
+    /**
+     * 휴가 정책 조회
+     * 없으면 기본값으로 생성
+     */
+    public function show(): LeavePolicy
+    {
+        $tenantId = $this->tenantId();
+
+        $policy = LeavePolicy::where('tenant_id', $tenantId)->first();
+
+        if (! $policy) {
+            $policy = LeavePolicy::createDefault($tenantId, $this->apiUserId());
+        }
+
+        return $policy;
+    }
+
+    /**
+     * 휴가 정책 업데이트
+     * 없으면 생성
+     */
+    public function update(array $data): LeavePolicy
+    {
+        $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
+
+        $policy = LeavePolicy::where('tenant_id', $tenantId)->first();
+
+        if ($policy) {
+            $policy->fill([
+                'standard_type' => $data['standard_type'] ?? $policy->standard_type,
+                'fiscal_start_month' => $data['fiscal_start_month'] ?? $policy->fiscal_start_month,
+                'fiscal_start_day' => $data['fiscal_start_day'] ?? $policy->fiscal_start_day,
+                'default_annual_leave' => $data['default_annual_leave'] ?? $policy->default_annual_leave,
+                'additional_leave_per_year' => $data['additional_leave_per_year'] ?? $policy->additional_leave_per_year,
+                'max_annual_leave' => $data['max_annual_leave'] ?? $policy->max_annual_leave,
+                'carry_over_enabled' => $data['carry_over_enabled'] ?? $policy->carry_over_enabled,
+                'carry_over_max_days' => $data['carry_over_max_days'] ?? $policy->carry_over_max_days,
+                'carry_over_expiry_months' => $data['carry_over_expiry_months'] ?? $policy->carry_over_expiry_months,
+                'updated_by' => $userId,
+            ]);
+            $policy->save();
+        } else {
+            $policy = LeavePolicy::create([
+                'tenant_id' => $tenantId,
+                'standard_type' => $data['standard_type'] ?? LeavePolicy::TYPE_FISCAL,
+                'fiscal_start_month' => $data['fiscal_start_month'] ?? 1,
+                'fiscal_start_day' => $data['fiscal_start_day'] ?? 1,
+                'default_annual_leave' => $data['default_annual_leave'] ?? 15,
+                'additional_leave_per_year' => $data['additional_leave_per_year'] ?? 1,
+                'max_annual_leave' => $data['max_annual_leave'] ?? 25,
+                'carry_over_enabled' => $data['carry_over_enabled'] ?? true,
+                'carry_over_max_days' => $data['carry_over_max_days'] ?? 10,
+                'carry_over_expiry_months' => $data['carry_over_expiry_months'] ?? 3,
+                'created_by' => $userId,
+                'updated_by' => $userId,
+            ]);
+        }
+
+        return $policy->fresh();
+    }
+}