feat: H-1 입고 관리 API 구현

- ReceivingController: CRUD 및 목록 조회 API
- ReceivingService: 입고 비즈니스 로직
- Receiving 모델: 다중 테넌트 지원
- FormRequest 검증 클래스
- Swagger 문서화
- receivings 테이블 마이그레이션

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

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

app/Models/Tenants/Receiving.php

@@ -0,0 +1,107 @@
+<?php
+
+namespace App\Models\Tenants;
+
+use App\Traits\BelongsToTenant;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\SoftDeletes;
+
+class Receiving extends Model
+{
+    use BelongsToTenant, SoftDeletes;
+
+    protected $fillable = [
+        'tenant_id',
+        'receiving_number',
+        'order_no',
+        'order_date',
+        'item_id',
+        'item_code',
+        'item_name',
+        'specification',
+        'supplier',
+        'order_qty',
+        'order_unit',
+        'due_date',
+        'receiving_qty',
+        'receiving_date',
+        'lot_no',
+        'supplier_lot',
+        'receiving_location',
+        'receiving_manager',
+        'status',
+        'remark',
+        'created_by',
+        'updated_by',
+        'deleted_by',
+    ];
+
+    protected $casts = [
+        'order_date' => 'date',
+        'due_date' => 'date',
+        'receiving_date' => 'date',
+        'order_qty' => 'decimal:2',
+        'receiving_qty' => 'decimal:2',
+        'item_id' => 'integer',
+    ];
+
+    /**
+     * 상태 목록
+     */
+    public const STATUSES = [
+        'order_completed' => '발주완료',
+        'shipping' => '배송중',
+        'inspection_pending' => '검사대기',
+        'receiving_pending' => '입고대기',
+        'completed' => '입고완료',
+    ];
+
+    /**
+     * 품목 관계
+     */
+    public function item(): BelongsTo
+    {
+        return $this->belongsTo(\App\Models\Items\Item::class);
+    }
+
+    /**
+     * 생성자 관계
+     */
+    public function creator(): BelongsTo
+    {
+        return $this->belongsTo(\App\Models\Members\User::class, 'created_by');
+    }
+
+    /**
+     * 상태 라벨
+     */
+    public function getStatusLabelAttribute(): string
+    {
+        return self::STATUSES[$this->status] ?? $this->status;
+    }
+
+    /**
+     * 수정 가능 여부
+     */
+    public function canEdit(): bool
+    {
+        return $this->status !== 'completed';
+    }
+
+    /**
+     * 삭제 가능 여부
+     */
+    public function canDelete(): bool
+    {
+        return $this->status !== 'completed';
+    }
+
+    /**
+     * 입고처리 가능 여부
+     */
+    public function canProcess(): bool
+    {
+        return in_array($this->status, ['order_completed', 'shipping', 'inspection_pending', 'receiving_pending']);
+    }
+}