feat(inventory): 強化調撥單功能，支援販賣機貨道欄位、開放商品重複加入及優化過帳庫存檢核

database/migrations/tenant/2026_02_09_163350_add_position_to_inventory_transfer_items.php

@@ -0,0 +1,28 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('inventory_transfer_items', function (Blueprint $table) {
+            $table->string('position')->nullable()->after('quantity')->comment('貨道/儲位');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('inventory_transfer_items', function (Blueprint $table) {
+            $table->dropColumn('position');
+        });
+    }
+};