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/Inventory/Models/Unit.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace App\Modules\Inventory\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Spatie\Activitylog\Traits\LogsActivity;
+use Spatie\Activitylog\LogOptions;
+
+class Unit extends Model
+{
+    use HasFactory, LogsActivity;
+
+    protected $fillable = ['name', 'abbreviation'];
+
+    public function productsAsBase(): HasMany
+    {
+        return $this->hasMany(Product::class, 'base_unit_id');
+    }
+
+    public function productsAsLarge(): HasMany
+    {
+        return $this->hasMany(Product::class, 'large_unit_id');
+    }
+
+    public function getActivitylogOptions(): LogOptions
+    {
+        return LogOptions::defaults()
+            ->logAll()
+            ->logOnlyDirty()
+            ->dontSubmitEmptyLogs();
+    }
+
+    public function tapActivity(\Spatie\Activitylog\Contracts\Activity $activity, string $eventName)
+    {
+        $properties = $activity->properties;
+        
+        $snapshot = $properties['snapshot'] ?? [];
+        $snapshot['name'] = $this->name;
+        $properties['snapshot'] = $snapshot;
+
+        $activity->properties = $properties;
+    }
+}