feat(API): Model 및 관계 추가

- HandoverReport, HandoverReportItem, HandoverReportManager 모델 추가
- SiteBriefing 모델 추가
- StructureReview, FcmSendLog, Position, Salary 수정
- Order 모델 정리

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

app/Models/Construction/HandoverReportManager.php

@@ -0,0 +1,77 @@
+<?php
+
+namespace App\Models\Construction;
+
+use App\Models\Members\User;
+use App\Traits\BelongsToTenant;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+/**
+ * 인수인계보고서 공사담당자 모델
+ *
+ * @property int $id
+ * @property int $tenant_id
+ * @property int $handover_report_id
+ * @property string $name
+ * @property string|null $non_performance_reason
+ * @property string|null $signature
+ * @property int $sort_order
+ * @property int|null $created_by
+ * @property int|null $updated_by
+ * @property \Illuminate\Support\Carbon|null $created_at
+ * @property \Illuminate\Support\Carbon|null $updated_at
+ */
+class HandoverReportManager extends Model
+{
+    use BelongsToTenant;
+
+    protected $table = 'handover_report_managers';
+
+    protected $fillable = [
+        'tenant_id',
+        'handover_report_id',
+        'name',
+        'non_performance_reason',
+        'signature',
+        'sort_order',
+        'created_by',
+        'updated_by',
+    ];
+
+    protected $casts = [
+        'sort_order' => 'integer',
+    ];
+
+    protected $attributes = [
+        'sort_order' => 0,
+    ];
+
+    // =========================================================================
+    // 관계 정의
+    // =========================================================================
+
+    /**
+     * 인수인계보고서
+     */
+    public function handoverReport(): BelongsTo
+    {
+        return $this->belongsTo(HandoverReport::class, 'handover_report_id');
+    }
+
+    /**
+     * 생성자
+     */
+    public function creator(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'created_by');
+    }
+
+    /**
+     * 수정자
+     */
+    public function updater(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'updated_by');
+    }
+}