Add hardcoded trial license key (#1649)

### Context
<!--- Why are your changes required? What problem do they solve? -->

https://app.clickup.com/t/9015210959/HF-116

### How did you test your changes?
<!--- Describe in detail how you tested your changes. -->

unit tests

### Types of changes
<!--- What types of changes does your code introduce? Put an `x` in each
box that applies. -->
- [ ] Breaking change (a fix or a feature because of which an existing
functionality doesn't work as expected anymore)
- [x] New feature or improvement (a non-breaking change that adds
functionality)
- [ ] Bug fix (a non-breaking change that fixes an issue)
- [ ] Additional language file, or a change to an existing language file
(translations)
- [ ] Change to the documentation

### Checklist:
<!--- Go through the points below, and put an `x` in each box that
applies. -->
<!--- If you're unsure about any of these, contact us. We're always glad
to help! -->
- [ ] I have reviewed the guidelines about [Contributing to
HyperFormula](https://hyperformula.handsontable.com/guide/contributing.html)
and I confirm that my code follows the code style of this project.
- [ ] I have signed the [Contributor License
Agreement](https://goo.gl/forms/yuutGuN0RjsikVpM2).
- [ ] My change is compliant with the
[OpenDocument](https://docs.oasis-open.org/office/OpenDocument/v1.3/os/part4-formula/OpenDocument-v1.3-os-part4-formula.html)
standard.
- [ ] My change is compatible with Microsoft Excel.
- [ ] My change is compatible with Google Sheets.
- [ ] I described my changes in the
[CHANGELOG.md](https://github.com/handsontable/hyperformula/blob/master/CHANGELOG.md)
file.
- [ ] My changes require a documentation update.
- [ ] My changes require a migration guide.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **High Risk**
> Updates license validation logic, a compliance-critical area, by
adding a hardcoded key that will always be treated as valid; mistakes
here could unintentionally bypass licensing checks.
> 
> **Overview**
> Adds a new hardcoded trial license key
(`hftrial-0168e-1f2b7-47158-70b05-0842f`) to the whitelist in
`checkLicenseKeyValidity`, causing that exact value to be treated as
`valid` without schema/expiry checks.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
fd095ae. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: sequba

src/helpers/licenseKeyValidator.ts

@@ -54,7 +54,7 @@ export function checkLicenseKeyValidity(licenseKey: string): LicenseKeyValidityS
     vars: {},
   }
 
-  if (licenseKey === 'gpl-v3' || licenseKey === 'internal-use-in-handsontable') {
+  if (licenseKey === 'gpl-v3' || licenseKey === 'internal-use-in-handsontable' || licenseKey === 'hftrial-0168e-1f2b7-47158-70b05-0842f') {
     messageDescriptor.template = LicenseKeyValidityState.VALID
 
   } else if (typeof licenseKey === 'string' && checkKeySchema(licenseKey)) {