新增單位管理以及一些功能修正

app/Models/Unit.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class Unit extends Model
+{
+    /** @use HasFactory<\Database\Factories\UnitFactory> */
+    use HasFactory;
+
+    protected $fillable = [
+        'name',
+        'code',
+    ];
+}