feat(시공사): 2.1 현장관리 - Backend API 확장

- 마이그레이션: site_code, client_id, status 컬럼 추가
- Site 모델: 상태 상수, Client 관계 추가
- SiteService: stats(), bulkDestroy(), 필터 확장
- SiteController: stats, bulkDestroy 엔드포인트 추가
- 라우트: /stats, /bulk 추가

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

app/Models/Tenants/Site.php

@@ -3,6 +3,7 @@
 namespace App\Models\Tenants;
 
 use App\Models\Members\User;
+use App\Models\Orders\Client;
 use App\Traits\BelongsToTenant;
 use App\Traits\ModelTrait;
 use Illuminate\Database\Eloquent\Model;
@@ -14,14 +15,18 @@
  *
  * @property int $id
  * @property int $tenant_id
+ * @property string|null $site_code 현장코드
+ * @property int|null $client_id 거래처 ID
  * @property string $name
  * @property string|null $address
  * @property float|null $latitude
  * @property float|null $longitude
  * @property bool $is_active
+ * @property string $status 상태: unregistered|suspended|active|pending
  * @property int|null $created_by
  * @property int|null $updated_by
  * @property int|null $deleted_by
+ * @property-read Client|null $client
  */
 class Site extends Model
 {
@@ -29,13 +34,32 @@ class Site extends Model
 
     protected $table = 'sites';
 
+    // 상태 상수
+    public const STATUS_UNREGISTERED = 'unregistered';
+
+    public const STATUS_SUSPENDED = 'suspended';
+
+    public const STATUS_ACTIVE = 'active';
+
+    public const STATUS_PENDING = 'pending';
+
+    public const STATUSES = [
+        self::STATUS_UNREGISTERED,
+        self::STATUS_SUSPENDED,
+        self::STATUS_ACTIVE,
+        self::STATUS_PENDING,
+    ];
+
     protected $fillable = [
         'tenant_id',
+        'site_code',
+        'client_id',
         'name',
         'address',
         'latitude',
         'longitude',
         'is_active',
+        'status',
         'created_by',
         'updated_by',
         'deleted_by',
@@ -49,6 +73,7 @@ class Site extends Model
 
     protected $attributes = [
         'is_active' => true,
+        'status' => self::STATUS_UNREGISTERED,
     ];
 
     // =========================================================================
@@ -71,6 +96,14 @@ public function updater(): BelongsTo
         return $this->belongsTo(User::class, 'updated_by');
     }
 
+    /**
+     * 거래처
+     */
+    public function client(): BelongsTo
+    {
+        return $this->belongsTo(Client::class);
+    }
+
     // =========================================================================
     // 헬퍼 메서드
     // =========================================================================