feat: add settings table and Setting model

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

app/Models/Setting.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+
+class Setting extends Model
+{
+    protected $fillable = ['key', 'value'];
+
+    public static function get(string $key, mixed $default = null): mixed
+    {
+        $setting = static::where('key', $key)->first();
+        return $setting ? $setting->value : $default;
+    }
+
+    public static function set(string $key, mixed $value): void
+    {
+        static::updateOrCreate(['key' => $key], ['value' => $value]);
+    }
+}