Users can now duplicate a signing template while keeping its existing signature fields and related signing items. This makes it easier to create similar documents without rebuilding the signing setup from scratch, saving time and reducing setup errors.

This feature allows reusing sign items from a determined template in other templates.

task-2541739

HR officers can now request several signatures at the same time for a single employee contract. This streamlines contract approval workflows for templates that require only the employee signature as well as those requiring both employee and manager signatures.

Allows a hr officer to request multiple signatures at once for the same
contract. Both employee only templates and employee+manager templates.

Task ID: 2563227

Belgian payroll users are now guided to correct employee document languages through a dedicated wizard instead of receiving a blocking error. This makes payroll processing smoother by letting teams fix affected employees directly when generating Belgian documents.

Previously if the language set on the address of an employee wasn't
correct (for belgian documents) an error would be thrown at the user
telling them to change the language.
After this commit, a wizard will be opened instead, allowing to change
the language of the problematic employees directly.

Task ID: 2582516

Sign administrators can now configure terms and conditions in settings. When enabled, those terms are automatically included at the bottom of signature request emails, either as text or as a link, helping companies communicate legal or policy requirements consistently.

This PR adds a terms and conditions fields in the settings of sign. If set, the settings are added to the bottom of the `sign_template_mail_request` email.

task-2541739