feat: [leave] 휴가관리 Phase 1 구현

- Leave, LeavePolicy, LeaveGrant 모델 생성
- LeaveBalance 헬퍼 메서드 추가 (useLeave, restoreLeave, canUse)
- LeaveService 핵심 로직 (신청, 승인, 반려, 취소, 잔여연차, 통계)
- API 컨트롤러 (목록, 등록, 승인/반려/취소, 잔여연차, 통계, CSV 내보내기)
- 뷰 컨트롤러 + 라우트 등록 (web, api)
- Blade 뷰 (index + 3개 탭 partials: table, balance, stats)

app/Http/Controllers/HR/LeaveController.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App\Http\Controllers\HR;
+
+use App\Http\Controllers\Controller;
+use App\Models\HR\Leave;
+use App\Services\HR\LeaveService;
+use Illuminate\Contracts\View\View;
+use Illuminate\Http\Response;
+
+class LeaveController extends Controller
+{
+    public function __construct(
+        private LeaveService $leaveService
+    ) {}
+
+    public function index(): View|Response
+    {
+        $employees = $this->leaveService->getActiveEmployees();
+        $departments = $this->leaveService->getDepartments();
+        $typeMap = Leave::TYPE_MAP;
+        $statusMap = Leave::STATUS_MAP;
+
+        return view('hr.leaves.index', [
+            'employees' => $employees,
+            'departments' => $departments,
+            'typeMap' => $typeMap,
+            'statusMap' => $statusMap,
+        ]);
+    }
+}