Add support for controller method pairs in routing

[CodeWithKyrian]

This PR adds support for using controller-method pairs in route definitions using array notation [Controller::class, 'method']. This enhancement allows developers to group related actions into controller classes while keeping the routing concise.

Changes

• Added callableMethod in Container class to handle controllers with named methods
• Enhanced RouteHandler::map to detect and support [ControllerClass::class, 'method'] syntax
• Added comprehensive test coverage for both the new container method and routing functionality
• Updated documentation to demonstrate the new capability

Benefits

• Better code organization: Group related endpoints into a single controller class
• Familiar syntax: Uses the standard PHP array callback notation
• Fully backward compatible: All existing code and patterns continue to work
• Middleware support: Controller methods can be used as both handlers and middleware

Example

// Before: 
$app->get('/users', UserListController::class);
$app->get('/users/{id}', UserShowController::class);
$app->post('/users', UserCreateController::class);
$app->delete('/users/{id}', UserDeleteController::class);

// After:
$app->get('/users', [UserController::class, 'index']);
$app->get('/users/{id}', [UserController::class, 'show']);
$app->post('/users', [UserController::class, 'create']);
$app->delete('/users/{id}', [UserController::class, 'delete']);

The implementation maintains the same dependency injection capabilities and performance characteristics as the existing approach with invokable controllers.