feat: H-2 재고 현황 API 구현

- StockController: 재고 조회 및 통계 API
- StockService: 재고 비즈니스 로직
- Stock, StockLot 모델: 재고/로트 관리
- Swagger 문서화
- stocks, stock_lots 테이블 마이그레이션

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

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

app/Http/Controllers/Api/V1/StockController.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace App\Http\Controllers\Api\V1;
+
+use App\Helpers\ApiResponse;
+use App\Http\Controllers\Controller;
+use App\Services\StockService;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+
+class StockController extends Controller
+{
+    public function __construct(
+        private readonly StockService $service
+    ) {}
+
+    /**
+     * 재고 목록 조회
+     */
+    public function index(Request $request): JsonResponse
+    {
+        $params = $request->only([
+            'search',
+            'item_type',
+            'status',
+            'location',
+            'sort_by',
+            'sort_dir',
+            'per_page',
+            'page',
+        ]);
+
+        $stocks = $this->service->index($params);
+
+        return ApiResponse::success($stocks, __('message.fetched'));
+    }
+
+    /**
+     * 재고 통계 조회
+     */
+    public function stats(): JsonResponse
+    {
+        $stats = $this->service->stats();
+
+        return ApiResponse::success($stats, __('message.fetched'));
+    }
+
+    /**
+     * 재고 상세 조회 (LOT 포함)
+     */
+    public function show(int $id): JsonResponse
+    {
+        try {
+            $stock = $this->service->show($id);
+
+            return ApiResponse::success($stock, __('message.fetched'));
+        } catch (\Illuminate\Database\Eloquent\ModelNotFoundException $e) {
+            return ApiResponse::error(__('error.stock.not_found'), 404);
+        }
+    }
+
+    /**
+     * 품목유형별 통계 조회
+     */
+    public function statsByItemType(): JsonResponse
+    {
+        $stats = $this->service->statsByItemType();
+
+        return ApiResponse::success($stats, __('message.fetched'));
+    }
+}