feat: Add user level and experience attributes, and implement reward, task, and quest models with corresponding controllers and migrations

backend/app/Models/Reward.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class Reward extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'name',
+        'description',
+        'unlocked_at_level'
+    ];
+
+    public function users()
+    {
+        return $this->belongsToMany(User::class, 'reward_user');
+    }
+}