search: add Search section calling arcadia-search admin sidecar

New /search route manages tenants and corpora on the arcadia-search
box via its privileged /admin/* surface (default :7801) — KPI tiles,
flat tenant×corpus table with Rebuild / Edit config / Delete
actions, New tenant / New corpus dialogs, and a Restart service
button. New app/lib/search-admin.ts wraps the bearer-token fetch.

Configured by VITE_ARCADIA_SEARCH_ADMIN_URL +
VITE_ARCADIA_SEARCH_ADMIN_TOKEN; the route renders a warning banner
when the token is unset. Token ships in the client bundle — fine for
this internal tool, called out in CLAUDE.md and the source comments.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/routes.ts

@@ -26,5 +26,6 @@ export default [
   route("sso", "routes/sso.tsx"),
   route("announcements", "routes/announcements.tsx"),
   route("status-page", "routes/status-page.tsx"),
+  route("search", "routes/search.tsx"),
   // CREMA:ROUTES
 ] satisfies RouteConfig