Add PHP 7.4+ support

[Copilot]

• Update composer.json: change PHP requirement from >=8.1.0 to >=7.4, add PHPUnit ^9.5 to dev requirement
• Update tests/DbQueryTest.php: replace #[Group('database')] attribute (PHP 8.0+) with @group database docblock annotation (compatible with PHPUnit 9+)
• Update phpunit.xml: remove cacheDirectory attribute (PHPUnit 10+ only) and <source> element (PHPUnit 10+ only) to be compatible with PHPUnit 9.x
• Update .github/workflows/tests.yml: add PHP 7.4 and 8.0 to the test matrix
• Fix PHP 7.4 test failures: change $value == 'true' to strict $value === 1 || $value === '1' || $value === 'true' in Tools::checkInput() — in PHP 7.4, 0 == 'true' incorrectly evaluated to true due to non-numeric strings being cast to 0 before loose integer comparison

Original prompt

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This section details on the original issue you should resolve

<issue_title>We must support php 7.4</issue_title>
<issue_description>Code is ancient; supporting 7.4 should be trivial.
Add a 7.4 test runner as well; perhaps add a bunch more versions between 7.4 and 8.0</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes We must support php 7.4 #3

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[daedeloth]

@copilot fix failing tests

[Copilot]

@copilot fix failing tests

Fixed in e158dc3. The failures were in testBoolCheckInput and testBoolGetInput — in PHP 7.4, 0 == 'true' evaluated to true because non-numeric strings were cast to 0 before loose integer comparison, making checkInput(0, 'bool') incorrectly return true. Fixed by switching to strict comparisons: $value === 1 || $value === '1' || $value === 'true'.