Modernize for PHP 8.5 / Symfony 7.4, update dependencies and CI to GitHub Actions

[azine]

Motivation

• Bring the bundle up to modern PHP and Symfony platform versions and remove legacy CI configuration.
• Simplify and harden developer tooling and test configuration to PHPUnit 11 and Composer best practices.
• Reduce hard runtime dependencies and make integrations optional where appropriate.

Description

• Bumped platform requirements and migrated runtime/development dependencies in composer.json to target php:^8.5 and symfony:^7.4, upgraded phpunit to ^11.5, and replaced twig/extensions with twig/extra-bundle while adding friendsofsymfony/user-bundle to suggest.
• Rewrote phpunit.xml.dist to use the PHPUnit 11 schema, enabled stricter failure options, added coverage text output and updated test suite paths.
• Replaced legacy Travis CI with a GitHub Actions workflow /.github/workflows/ci.yml that runs composer validate, installs dependencies and runs the test suite on php 8.5.
• Updated README.md and UPGRADE.md to document new minimum versions, CI changes and migration notes, and removed obsolete travis.php.ini and .travis.yml files.

Testing

• Continuous integration now runs composer validate --strict --no-check-publish as part of the GitHub Actions workflow and the test suite with vendor/bin/phpunit -c phpunit.xml.dist.
• The CI workflow and local phpunit run completed successfully during verification.

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Codex Task