Bump min PHP version to 8.1

[Jeckerson]

No description provided.

[Copilot]

Pull Request Overview

This PR upgrades the minimum PHP version requirement from 7.4 to 8.1, modernizing the codebase to leverage PHP 8.1 features. The changes include migrating from Codeception to PHPUnit for testing, adding PHP 8.1's #[\Override] attributes to interface implementations, updating method signatures to use proper return types (particularly for the gc() method), and consolidating the test structure into a simplified hierarchy.

Key changes:

• Minimum PHP version bumped to 8.1 in composer.json and Docker configuration
• Test framework migrated from Codeception to PHPUnit with consolidated test files
• Method signatures updated with #[\Override] attributes and PHP 8.1+ type declarations
• CI/CD workflow consolidated into a single pipeline with updated tooling versions

Reviewed Changes

Copilot reviewed 26 out of 29 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
composer.json	Updated minimum PHP to 8.1, replaced Codeception with PHPUnit, upgraded dev dependencies
src/Adapter/Mongo.php	Added #[\Override] attributes, updated gc() return type to int|false, renamed parameters
src/Adapter/Database.php	Added #[\Override] attributes, updated gc() return type to int|false, improved return logic
tests/Adapter/MongoTest.php	New consolidated PHPUnit test replacing Codeception unit and functional tests
tests/Adapter/DatabaseTest.php	Migrated from Codeception to PHPUnit with setUp/tearDown lifecycle methods
.github/workflows/main.yml	Consolidated CI workflow combining validations and tests, updated PHP versions tested
.docker/Dockerfile	Updated base image to PHP 8.1 with compilation flags for Phalcon extension
phpunit.xml	New PHPUnit configuration file replacing Codeception setup
psalm.xml	Simplified static analysis configuration with stricter error level
phpcs.xml.dist	Added tests directory to code style validation

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