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/Models/Tenants/LeavePolicy.php

@@ -0,0 +1,127 @@
+<?php
+
+namespace App\Models\Tenants;
+
+use App\Traits\BelongsToTenant;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+/**
+ * 휴가 정책 모델
+ *
+ * @property int $id
+ * @property int $tenant_id
+ * @property string $standard_type
+ * @property int $fiscal_start_month
+ * @property int $fiscal_start_day
+ * @property int $default_annual_leave
+ * @property int $additional_leave_per_year
+ * @property int $max_annual_leave
+ * @property bool $carry_over_enabled
+ * @property int $carry_over_max_days
+ * @property int $carry_over_expiry_months
+ * @property int|null $created_by
+ * @property int|null $updated_by
+ */
+class LeavePolicy extends Model
+{
+    use BelongsToTenant;
+
+    protected $table = 'leave_policies';
+
+    protected $fillable = [
+        'tenant_id',
+        'standard_type',
+        'fiscal_start_month',
+        'fiscal_start_day',
+        'default_annual_leave',
+        'additional_leave_per_year',
+        'max_annual_leave',
+        'carry_over_enabled',
+        'carry_over_max_days',
+        'carry_over_expiry_months',
+        'created_by',
+        'updated_by',
+    ];
+
+    protected $casts = [
+        'fiscal_start_month' => 'integer',
+        'fiscal_start_day' => 'integer',
+        'default_annual_leave' => 'integer',
+        'additional_leave_per_year' => 'integer',
+        'max_annual_leave' => 'integer',
+        'carry_over_enabled' => 'boolean',
+        'carry_over_max_days' => 'integer',
+        'carry_over_expiry_months' => 'integer',
+    ];
+
+    // =========================================================================
+    // 상수 정의
+    // =========================================================================
+
+    public const TYPE_FISCAL = 'fiscal';
+
+    public const TYPE_HIRE = 'hire';
+
+    public const STANDARD_TYPES = [
+        self::TYPE_FISCAL,
+        self::TYPE_HIRE,
+    ];
+
+    // =========================================================================
+    // 관계 정의
+    // =========================================================================
+
+    /**
+     * 테넌트
+     */
+    public function tenant(): BelongsTo
+    {
+        return $this->belongsTo(Tenant::class);
+    }
+
+    // =========================================================================
+    // 헬퍼 메서드
+    // =========================================================================
+
+    /**
+     * 기준 유형 라벨
+     */
+    public function getStandardTypeLabelAttribute(): string
+    {
+        return match ($this->standard_type) {
+            self::TYPE_FISCAL => '회계연도',
+            self::TYPE_HIRE => '입사일',
+            default => $this->standard_type,
+        };
+    }
+
+    /**
+     * 기준일 문자열
+     */
+    public function getFiscalStartDateStringAttribute(): string
+    {
+        return "{$this->fiscal_start_month}월 {$this->fiscal_start_day}일";
+    }
+
+    /**
+     * 기본 설정 생성
+     */
+    public static function createDefault(int $tenantId, ?int $userId = null): self
+    {
+        return self::create([
+            'tenant_id' => $tenantId,
+            'standard_type' => self::TYPE_FISCAL,
+            'fiscal_start_month' => 1,
+            'fiscal_start_day' => 1,
+            'default_annual_leave' => 15,
+            'additional_leave_per_year' => 1,
+            'max_annual_leave' => 25,
+            'carry_over_enabled' => true,
+            'carry_over_max_days' => 10,
+            'carry_over_expiry_months' => 3,
+            'created_by' => $userId,
+            'updated_by' => $userId,
+        ]);
+    }
+}