feat(API): Position API 추가 (직급/직책 통합)

- Position 모델 생성 (type: rank | title)
- PositionService: CRUD + reorder 구현
- PositionController: REST API 엔드포인트
- Swagger 문서 작성 (PositionApi.php)
- 마이그레이션: positions 테이블 + common_codes 등록
- routes/api.php에 라우트 등록

Phase L-3 (직급관리), L-4 (직책관리) 백엔드 완료

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

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

app/Models/Tenants/Position.php

@@ -0,0 +1,75 @@
+<?php
+
+namespace App\Models\Tenants;
+
+use App\Traits\BelongsToTenant;
+use App\Traits\ModelTrait;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\SoftDeletes;
+
+/**
+ * 직급/직책 통합 모델
+ *
+ * @property int $id
+ * @property int $tenant_id
+ * @property string $type rank(직급) | title(직책)
+ * @property string $name 명칭
+ * @property int $sort_order 정렬 순서
+ * @property bool $is_active 활성화 여부
+ */
+class Position extends Model
+{
+    use BelongsToTenant, ModelTrait, SoftDeletes;
+
+    protected $table = 'positions';
+
+    protected $fillable = [
+        'tenant_id',
+        'type',
+        'name',
+        'sort_order',
+        'is_active',
+    ];
+
+    protected $casts = [
+        'tenant_id' => 'int',
+        'sort_order' => 'int',
+        'is_active' => 'bool',
+    ];
+
+    protected $hidden = [
+        'deleted_at',
+    ];
+
+    // =========================================================================
+    // 상수
+    // =========================================================================
+
+    public const TYPE_RANK = 'rank';   // 직급
+
+    public const TYPE_TITLE = 'title'; // 직책
+
+    // =========================================================================
+    // 스코프
+    // =========================================================================
+
+    public function scopeRanks($query)
+    {
+        return $query->where('type', self::TYPE_RANK);
+    }
+
+    public function scopeTitles($query)
+    {
+        return $query->where('type', self::TYPE_TITLE);
+    }
+
+    public function scopeActive($query)
+    {
+        return $query->where('is_active', true);
+    }
+
+    public function scopeOrdered($query)
+    {
+        return $query->orderBy('sort_order');
+    }
+}