feat: add Laravel 11/12 and PHP 8.3+ support

- Widen illuminate/* deps to ^10.0|^11.0|^12.0, require PHP ^8.3
- Upgrade PHPUnit to ^10.5|^11.0, Mockery to ^1.6
- Rewrite phpunit.xml.dist for PHPUnit 10+ format (source/include
  replaces filter/whitelist, removed deprecated attributes)
- Replace $dates with $casts on Token model
- Implement DeferrableProvider interface instead of $defer property
  on ClientServiceProvider
- Use FQCN route definitions instead of string-based namespace()
- Fix migration getColumnType() check for Laravel 11+ native types
- Replace @test doc annotations with #[Test] attributes
- Fix dynamic property deprecation in ControllerTest

src/Token.php

@@ -34,11 +34,14 @@ class Token extends Model
     protected $table = 'quickbooks_tokens';
 
     /**
-     * The attributes that should be mutated to dates.
+     * The attributes that should be cast.
      *
-     * @var array
+     * @var array<string, string>
      */
-    protected $dates = ['access_token_expires_at', 'refresh_token_expires_at'];
+    protected $casts = [
+        'access_token_expires_at' => 'datetime',
+        'refresh_token_expires_at' => 'datetime',
+    ];
 
     /**
      * The attributes that are mass assignable.