Support Multiple Labour Price Books

Feature Request: Enable multiple Labour Price Books, similar to the existing Hardware Price Books functionality.

This would allow organisations to maintain different labour rates for varying customer types, regions, contracts, business units, or pricing strategies, while using the appropriate price book for each project.

Currently, labour pricing is limited to a single price book, unlike hardware pricing. Bringing labour pricing in line with hardware price books would provide greater pricing flexibility, consistency, and scalability for organisations with diverse service offerings.