Retrieve companies for an organisation node.
Use recursive=true (default) to include all companies in the subtree, or recursive=false to get only companies directly assigned to this node.
Supports filtering by company_id for access validation purposes.
Supports pagination with page[number] and page[size] parameters.

🔒 External clients call this endpoint with an OAC (Organisation Access Credentials — ⚠️ Beta) access token carrying the organisations:read and companies:read scopes.

Access validation: The OAC token's organisation_node must be an ancestor of (or equal to) the requested node.