feat: integrate PHPStan, Rector and Pint code quality tools (#13)

* feat: integrate PHPStan, Rector and Pint code quality tools

- Add larastan, rector, and rector-laravel dev dependencies
- Configure PHPStan at max level with Larastan extension
- Configure Rector with Laravel sets and code quality rules
- Configure Pint with strict rules (final_class, strict_types)
- Add composer scripts: lint, test:lint, test:types, test:unit
- Add GitHub Actions workflow for CI on push/PR
- Apply code style fixes across all files

* docs: add code quality section to README

app/Models/User.php

@@ -1,17 +1,34 @@
 <?php
 
+declare(strict_types=1);
+
 namespace App\Models;
 
 // use Illuminate\Contracts\Auth\MustVerifyEmail;
+use Database\Factories\UserFactory;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Foundation\Auth\User as Authenticatable;
 use Illuminate\Notifications\Notifiable;
+use Illuminate\Support\Carbon;
 use Laravel\Sanctum\HasApiTokens;
 
-class User extends Authenticatable
+/**
+ * @property int $id
+ * @property string $name
+ * @property string $email
+ * @property Carbon|null $email_verified_at
+ * @property string $password
+ * @property Carbon|null $created_at
+ * @property Carbon|null $updated_at
+ */
+final class User extends Authenticatable
 {
-    /** @use HasFactory<\Database\Factories\UserFactory> */
-    use HasApiTokens, HasFactory, Notifiable;
+    use HasApiTokens;
+
+    /** @use HasFactory<UserFactory> */
+    use HasFactory;
+
+    use Notifiable;
 
     /**
      * The attributes that are mass assignable.