refactor(admin/members): dedupe STATUS_LABELS + reactive row update

Promote inline STATUS_LABELS copies (admin/members/index.vue,
member/account.vue) into app/config/memberStatus.js, matching the
app/config/circles.js pattern. Drive admin/members/[id].vue status
select from the same constant — completes the alignment started in
441a5f5.

Use the softer member-facing copy as canonical: "Paused" / "Closed"
instead of "Suspended" / "Cancelled".

Also fix markSlackInvited's non-reactive Object.assign on a plain
object inside a useFetch array — replace with index-find + element
reassignment so the row UI refreshes without a manual reload.

app/config/memberStatus.js

@@ -0,0 +1,8 @@
+export const STATUS_LABELS = {
+  active: "Active",
+  pending_payment: "Payment setup incomplete",
+  suspended: "Paused",
+  cancelled: "Closed",
+};
+
+export const statusLabel = (s) => STATUS_LABELS[s] || "Pending";