chore: add php-cs-fixer with PSR-12 config and CI check

- Add friendsofphp/php-cs-fixer to require-dev
- Create .php-cs-fixer.dist.php configured for @PSR12 ruleset
- Add php-cs-fixer dry-run step to CI pipeline
- Auto-fix existing PSR-12 violations
- Document code style tooling in readme.md

tests/Unit/Enum/ScopeTest.php

@@ -1,4 +1,5 @@
 <?php
+
 declare(strict_types=1);
 
 namespace App\Tests\Unit\Enum;
@@ -6,20 +7,24 @@ namespace App\Tests\Unit\Enum;
 use App\Enum\Scope;
 use PHPUnit\Framework\TestCase;
 
-final class ScopeTest extends TestCase {
-    public function testCases(): void {
+final class ScopeTest extends TestCase
+{
+    public function testCases(): void
+    {
         self::assertSame('cookie', Scope::Cookie->value);
         self::assertSame('ip', Scope::Ip->value);
         self::assertSame('none', Scope::None->value);
     }
 
-    public function testTryFromValid(): void {
+    public function testTryFromValid(): void
+    {
         self::assertSame(Scope::Cookie, Scope::tryFrom('cookie'));
         self::assertSame(Scope::Ip, Scope::tryFrom('ip'));
         self::assertSame(Scope::None, Scope::tryFrom('none'));
     }
 
-    public function testTryFromInvalid(): void {
+    public function testTryFromInvalid(): void
+    {
         self::assertNull(Scope::tryFrom('invalid'));
         self::assertNull(Scope::tryFrom(''));
     }