Rebrand: Co-op Check-in -> Co-op Survey in user-facing copy

Updates the tool product name across the app UI (header, page title,
section labels, form buttons, success/error states, report stat labels),
README, deployment docs, and the CiviCRM email template guidance.
Custom domain references move from check-in.fci.coop to survey.fci.coop
(DNS update still required).

The underlying CiviCRM "Check-in (organizing)" activity type, custom
group machine names (Check_in_data__organizing_), health-check ids,
and the internal org_engagement_check_in form id are unchanged --
those are CiviCRM contract surfaces, not product copy.

components/SiteChrome.tsx

@@ -19,7 +19,7 @@ export function SiteHeader() {
             className="h-12 w-auto sm:h-14"
           />
           <span className="hidden text-[11px] uppercase tracking-[0.18em] text-ink-mute sm:inline-block sm:border-l sm:border-rule sm:pl-4">
-            Co-op Check-in
+            Co-op Survey
           </span>
         </Link>
         <nav aria-label="Primary">