Modernize skeleton to PHP 8.2+, PSR-12, and PHPUnit 11/12

[jasdeepkhalsa]

Summary

This project hadn't moved since the PHP 5.4/PHPUnit 3.7 era. This PR brings it up to date: modern PHP (8.2+), PSR-4 autoloading, PSR-12 code style, current PHPUnit (11/12), and a GitHub Actions pipeline — using DBDiff as a reference for what a modern PHP project in this org looks like (PSR-4 layout, composer scripts, GitHub Actions matrix).

• Dependencies: phpunit/phpunit bumped from the long-EOL 3.7.* to ^11.0 || ^12.0. Dropped phpunit/dbunit and phpunit/phpunit-selenium — both abandoned packages that the skeleton never actually used, and both irrelevant to a plain unit-testing starter kit.
• Autoloading: PSR-0 → PSR-4. lib/Application/Example.php and tests/Application/ExampleTest.php flattened to lib/Example.php and tests/ExampleTest.php so the namespace root maps 1:1 onto the source directory (same convention DBDiff uses for its src/ tree), instead of duplicating the namespace name as a subdirectory.
• Code: declare(strict_types=1), scalar/union type hints, PSR-12 formatting. Tests converted to PHPUnit's attribute-based #[DataProvider] and expectException() — the old @dataProvider/@expectedException doc-comment annotations and the PHPUnit_Framework_TestCase base class no longer exist in current PHPUnit.
• phpunit.xml: updated to the PHPUnit 11 schema, <coverage><include> replaced with the current <source><include> block.
• Tooling: added PHP-CS-Fixer (PSR-12 ruleset) with composer cs-check/cs-fix scripts.
• CI: replaced .travis.yml (PHP 5.4/5.5/5.6, all long past EOL and unpatched) with .github/workflows/tests.yml, testing PHP 8.2–8.4 and running composer validate, the CS check, and the test suite on every push/PR.

Security

• Removed the composer.phar binary that was committed directly to the repo — a stale, unpatched executable checked into version control is itself a supply-chain risk; CI now installs Composer via the setup-php action's tool cache instead.
• Dropped phpunit/dbunit and phpunit/phpunit-selenium, both abandoned/unmaintained dev dependencies that unnecessarily widened the install's attack surface.
• Pushing this branch surfaced a GitHub Dependabot alert (1 high severity) against the previous composer.json on master — consistent with known CVEs in the ancient PHPUnit 3.7.x line this PR removes. The alert should clear automatically once this merges, since the vulnerable version constraint no longer exists on the branch.
• composer audit against the new dependency set (phpunit/phpunit, friendsofphp/php-cs-fixer) reports no known vulnerability advisories.
• No secrets, credentials, or hardcoded tokens found anywhere in the repository.

Test plan

• composer validate --strict passes with no warnings
• composer install resolves cleanly, PSR-4 autoload generates with zero "does not comply" warnings
• composer test (./vendor/bin/phpunit) — 4 tests, 4 assertions, all green
• composer cs-check (PHP-CS-Fixer dry-run) — 0 files need fixing
• composer audit — no advisories found
• CI workflow will validate the PHP 8.2/8.3/8.4 matrix once this PR is opened