chore(deps): move phpstan/phpdoc-parser to require-dev

Our code never uses PHPStan\PhpDocParser directly; the direct ^2.0 constraint
exists only so PHPStan's RuleTestCase resolves the same parser major as the
bundled phpstan.phar (a dev-tooling concern). It stays installed in prod as a
transitive of phpdocumentor/reflection-docblock, so production is unchanged —
only the redundant direct prod declaration moves to require-dev.

Addresses review feedback on #477.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: turegjorup

composer.json

@@ -29,7 +29,6 @@
         "nelmio/cors-bundle": "^2.1",
         "pentatrion/vite-bundle": "^8.1",
         "phpdocumentor/reflection-docblock": "^5.2",
-        "phpstan/phpdoc-parser": "^2.0",
         "rlanvin/php-rrule": "^2.2",
         "symfony/asset": "~6.4.0",
         "symfony/console": "~6.4.0",
@@ -58,6 +57,7 @@
         "friendsofphp/php-cs-fixer": "^3.0",
         "hautelook/alice-bundle": "^2.9",
         "phpstan/extension-installer": "^1.4",
+        "phpstan/phpdoc-parser": "^2.0",
         "phpstan/phpstan": "^2.1",
         "phpstan/phpstan-doctrine": "^2.0",
         "phpstan/phpstan-symfony": "^2.0",