* Add validation functionality

* Replace "Validations" with "Rules", add script-based validations and add docs

* Add asynchronous validation support and refactor validation methods removing unused operation parameter

* Remove unused `CommandOperation` parameter from `ValidateFieldsAsync` setups in `FormServiceTests`.

* Add support for "Run On" options for form rules

* Rename `IValidationScriptExecutor` to `IRuleExecutor` and refactor related services and tests accordingly

* Refactor validation methods: simplify `ValidateFieldsAsync` signatures and remove obsolete overloads

* Update `FieldValidationServiceTests` to use nullable types in test parameters

* Refactor `FormServiceTests` to use nullable types in test parameters and update mock setups accordingly

* Add support for "Run On Before Import" option in form rules and update corresponding services, models, and tests

* Set default value of `RunOnBeforeImport` to `true` in `FormElementRule` model

* Rename "Run On" operation properties to include "Before" prefix across models, resources, and views to improve clarity and consistency.

* Merge with main

* Update NCalc to 6.1.0

* Update layout