Assign or unassign a list for one unlocked combolist credential

Assign a specific unlocked list to a single unlocked combolist credential, or unassign it.

Behavior

• Provide list_id to assign. Use null to remove the assignment.
• Lists are shared with unlocked leaks: the same list can hold records from both datasets. Counts per dataset are read from GET /profile/unlocked/lists?dataset=combolist.