Add GetPublicBusinessInfo endpoint for non-admin users. Add URL validation for website_url. Add length/bounds validation for name, address, phone, email, VAT number. Retroactively apply VAT to past payments/till sales when is_vat_registered is enabled. Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>