Slider: improved value fallback handling + validation

[nielslyngsoe]

Improved slider value handling to accept a value to be 0 without doing a fallback. Plus validation implementation.

[Copilot]

Pull Request Overview

This PR improves the slider property editor's value handling to properly accept 0 values without fallback issues and adds comprehensive validation.

• Enhanced value fallback logic to treat 0 as a valid value instead of triggering fallback behavior
• Added proper validation for range overflow, underflow, and configuration errors
• Refactored type definitions to use interfaces for better type safety

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
types.ts	Adds interface definition for slider value object
property-editor-ui-slider.element.ts	Implements form validation mixin and improves value handling logic
input-slider.element.ts	Adds validation rules and refactors value property handling
input-number-range.element.ts	Updates error message to use localization key
localization.controller.ts	Adds documentation examples for the term method
en.ts	Adds new localization key for range validation error