Storefront: include child companies / multi-select when whitelisting companies

Description: We need a way to add multiple companies to our customer storefront at once, rather than adding them individually. Currently, when whitelisting companies for storefront access, we can only add them one at a time, which is impractical at scale.

Use case: We have parent companies with thousands of child companies that need access to the storefront. Adding each one individually would require thousands of separate actions, making this workflow prohibitively time-consuming and error-prone.

Proposed solution:

• A toggle to "Include child companies" when selecting a parent company for the storefront whitelist, automatically granting access to all child entities.
• Multi-select in the company dropdown to add multiple companies in a single action when only specific companies need access.

Expected benefit: Storefront access can be managed at scale without manual one-by-one configuration, reducing setup time from hours to minutes and making the storefront practical for organizations with large numbers of subsidiary accounts.