feat: 견적 단가 자동 적용 기능 추가

- 고객 그룹별 단가 조정 지원
- 견적 생성 시 자동 단가 조회
- 매출단가만 사용 (매입단가는 경고)

app/Models/Products/PriceHistory.php

@@ -2,6 +2,8 @@
 
 namespace App\Models\Products;
 
+use App\Models\Orders\ClientGroup;
+use App\Traits\BelongsToTenant;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\SoftDeletes;
 
@@ -10,6 +12,74 @@
  */
 class PriceHistory extends Model
 {
-    use SoftDeletes;
-    protected $fillable = ['tenant_id','item_type_code','item_id','price_type_code','price','started_at','ended_at'];
+    use BelongsToTenant, SoftDeletes;
+
+    protected $fillable = [
+        'tenant_id',
+        'item_type_code',
+        'item_id',
+        'price_type_code',
+        'client_group_id',
+        'price',
+        'started_at',
+        'ended_at',
+        'created_by',
+        'updated_by',
+        'deleted_by',
+    ];
+
+    protected $casts = [
+        'price' => 'decimal:4',
+        'started_at' => 'date',
+        'ended_at' => 'date',
+    ];
+
+    // ClientGroup 관계
+    public function clientGroup()
+    {
+        return $this->belongsTo(ClientGroup::class, 'client_group_id');
+    }
+
+    // Polymorphic 관계 (item_type_code에 따라 Product 또는 Material)
+    public function item()
+    {
+        if ($this->item_type_code === 'PRODUCT') {
+            return $this->belongsTo(Product::class, 'item_id');
+        } elseif ($this->item_type_code === 'MATERIAL') {
+            return $this->belongsTo(\App\Models\Materials\Material::class, 'item_id');
+        }
+
+        return null;
+    }
+
+    // 스코프
+    public function scopeForItem($query, string $itemType, int $itemId)
+    {
+        return $query->where('item_type_code', $itemType)
+            ->where('item_id', $itemId);
+    }
+
+    public function scopeForClientGroup($query, ?int $clientGroupId)
+    {
+        return $query->where('client_group_id', $clientGroupId);
+    }
+
+    public function scopeValidAt($query, $date)
+    {
+        return $query->where('started_at', '<=', $date)
+            ->where(function ($q) use ($date) {
+                $q->whereNull('ended_at')
+                    ->orWhere('ended_at', '>=', $date);
+            });
+    }
+
+    public function scopeSalePrice($query)
+    {
+        return $query->where('price_type_code', 'SALE');
+    }
+
+    public function scopePurchasePrice($query)
+    {
+        return $query->where('price_type_code', 'PURCHASE');
+    }
 }