fix: forward the visitor address on route-cached renders

Nitro's cached handler renders from a header-less copy of the request, so
under swr route rules useJournalApi, /rss.xml and the sitemap source
forwarded only the Nuxt peer and every cache miss shared one Journal API
rate-limit bucket (deferred in Phase 16). A Nitro plugin records
x-forwarded-for plus the peer in event.context.journalForwardedFor on the
request hook; the three callers forward it. Same key as the host app's
workaround, which keeps working. The acme SSR smoke's x-forwarded-for check
on the now route-cached playground is the test.

server/api/__sitemap__/journal.ts

@@ -15,9 +15,13 @@ export default defineSitemapEventHandler(async (event) => {
   const base = (config.journal as { apiBase: string }).apiBase
   const routes = (config.public.journal as { routes: JournalRoutes }).routes
 
-  const forwarded = [getRequestHeader(event, 'x-forwarded-for'), getRequestIP(event)]
-    .filter((v): v is string => typeof v === 'string' && v !== '')
-    .join(', ')
+  // Recorded by server/plugins/journal-client-address.ts before any route
+  // cache hides the request headers.
+  const forwarded =
+    (event.context.journalForwardedFor as string | undefined) ||
+    [getRequestHeader(event, 'x-forwarded-for'), getRequestIP(event)]
+      .filter((v): v is string => typeof v === 'string' && v !== '')
+      .join(', ')
   const headers: Record<string, string> = forwarded ? { 'x-forwarded-for': forwarded } : {}
   const fetcher: JournalFetcher = (path, query) => $fetch(path, { baseURL: base, query, headers })
   const api = createJournalClient(fetcher)