Support Container config with union types and intersection types

[clue]

This changeset adds support for Container config with union types (PHP 8.0+) and intersection types (PHP 8.1+) and DNF types (PHP 8.2+). With these changes applied, factory functions may now explicitly use advanced type features introduced in recent PHP versions, which is especially useful for string environment variable resolution:

$container = new FrameworkX\Container([
    AccessLogHandler => fn(bool|string $LOG = true) => new AccessLogHandler($LOG ? null : '/dev/null')
]);

Note that this does not affect default autowiring if no explicit factory function is used. This includes a number of updated tests to verify correct behavior and avoid introducing any potential regressions, so this has 100% code coverage and should be safe to apply. On top of this, I've updated the documentation slightly to emphasize environment variables are always of type string currently. This is the next step in adding better configuration support and support for environment variables and .env (dotenv) files as discussed in #101.

Builds on top of #286, #284, #184, #92, and others

[Copilot]

Pull request overview

This PR adds support for advanced PHP type features in the Container configuration, specifically union types (PHP 8.0+), intersection types (PHP 8.1+), and DNF (Disjunctive Normal Form) types (PHP 8.2+). This enhancement allows factory functions to use these modern type hints for better type safety and flexibility, particularly useful for environment variable resolution.

Key Changes:

• Refactored Container::validateType() to recursively handle union, intersection, and DNF types instead of rejecting them
• Updated error messages to be more descriptive when type mismatches occur
• Added comprehensive test coverage for all new type features

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/Container.php	Removed early abort for union/intersection types; enhanced validateType() to recursively check complex types; updated typeName() to handle non-named types
tests/ContainerTest.php	Added new tests for union, intersection, and DNF types; updated existing test names and error message expectations to reflect new behavior
tests/AppTest.php	Updated error messages for invalid constructor types to match new error format
docs/best-practices/controllers.md	Updated documentation to clarify that environment variables are strings and may require union types or casting

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