Upgrade PHP dependencies and move to Pest 5

Pest 5.1 brings PHPUnit 13.3; phpunit.xml and the tests needed no
changes. Everything else stays within its existing constraint: Laravel
13.31, Livewire 4.4.4, Octane 2.19.1, Fortify 1.39, Mary 2.9.10, Boost
2.8 and Pint 1.32. Guzzle moves to 8.2 as a transitive dependency.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017XYnWFt9pJEwvAmNFN38XD

composer.json

@@ -25,8 +25,8 @@
         "laravel/sail": "^1.41",
         "mockery/mockery": "^1.6",
         "nunomaduro/collision": "^8.6",
-        "pestphp/pest": "^4.3",
+        "pestphp/pest": "^5.1",
-        "pestphp/pest-plugin-laravel": "^4.0"
+        "pestphp/pest-plugin-laravel": "^5.0"
     },
     "autoload": {
         "psr-4": {