Membership Guardrails and Fixes

Membership preview is now blocked when Stripe is not configured for a partner, with a clear message and link to Stripe settings instead of opaque errors.

Data Import integration cards in Settings now stack on smaller screens instead of squishing.

Membership plan options (E+, Priority, Proactive, Signature) now appear in a consistent order in both Client Gateway and Portal Settings preview.

Fixed inability to delete a membership feature when it is still referenced by an active membership; the UI now prevents or handles this case.

Fixed Partner tab Memberships list showing features that are not enabled for a plan; only enabled features for each plan are shown.

Fixed notification failures when a conversation is merged or closed; status-change notifications no longer error when the conversation has been soft-deleted.