chore: 完善模組化架構遷移與修復前端顯示錯誤

- 修正所有模組 Controller 的 Model 引用路徑 (App\Modules\...)
- 更新 ProductionOrder 與 ProductionOrderItem 模型結構以符合新版邏輯
- 修復 resources/js/utils/format.ts 在處理空值時導致 toLocaleString 崩潰的問題
- 清除全域路徑與 Controller 遷移殘留檔案

app/Modules/Production/Models/ProductionOrderItem.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace App\Modules\Production\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use App\Modules\Inventory\Models\Product;
+
+class ProductionOrderItem extends Model
+{
+    /** @use HasFactory<\Database\Factories\ProductionOrderItemFactory> */
+    use HasFactory;
+
+    protected $fillable = [
+        'production_order_id',
+        'inventory_id',
+        'quantity_used',
+        'unit_id',
+    ];
+
+    protected $casts = [
+        'quantity_used' => 'decimal:4',
+    ];
+
+    public function inventory()
+    {
+        return $this->belongsTo(\App\Modules\Inventory\Models\Inventory::class);
+    }
+
+    public function unit()
+    {
+        return $this->belongsTo(\App\Modules\Inventory\Models\Unit::class);
+    }
+
+    public function productionOrder(): \Illuminate\Database\Eloquent\Relations\BelongsTo
+    {
+        return $this->belongsTo(ProductionOrder::class);
+    }
+
+    public function product(): \Illuminate\Database\Eloquent\Relations\BelongsTo
+    {
+        return $this->belongsTo(Product::class);
+    }
+}