Adds useSheetScopeEntityId hook used by both AttachProductSheet and
CreateScheduleSheet, which seeds scope from ?entity_id= and falls back
to the customer's active entity-level plan when no customer-level plan
exists. AttachFormProvider now exposes entityId and onScopeChange on
context, so AttachProductSelection and the scope dropdown pull from
the form context instead of the page-level useEntity() store.
Made-with: Cursor
d4907e63f2