backend: align API/models with current PostgreSQL schema

app/Models/Amenity.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+
+class Amenity extends Model
+{
+    use HasFactory;
+
+    public $timestamps = false;
+
+    protected $fillable = [
+        'name',
+    ];
+}