feat: FaqBlock layer for the SummerCMS FAQ API

- typed client and useFaq/useFaqApi (SSR, faq:<slug>:<locale> key,
  server and public bases, x-forwarded-for forwarded also on cached renders)
- FaqBlock, FaqList and FaqItem: native details, exclusive and openFirst,
  server-sanitized description and answers, nothing or #fallback on 404,
  error or no items
- FAQ tokens and base CSS with the .faq-html rules, README
- node client tests and a playground SSR smoke against a fixture API

server/plugins/faq-client-address.ts

@@ -0,0 +1,17 @@
+// Keeps the visitor's address available to route-cached SSR renders.
+//
+// An app rule such as `'/**': { swr }` renders cached pages from a copy of
+// the request without headers. The FAQ API throttles per client address,
+// so forwarding only the Nuxt peer would put every cache miss in one bucket.
+// The event context is shared with that copy, so the incoming
+// x-forwarded-for plus the peer address is recorded here, before the cached
+// handler runs, and useFaqApi forwards it.
+
+export default defineNitroPlugin((nitroApp) => {
+  nitroApp.hooks.hook('request', (event) => {
+    const forwarded = [getRequestHeader(event, 'x-forwarded-for'), event.node.req.socket?.remoteAddress]
+      .filter((v): v is string => typeof v === 'string' && v !== '')
+      .join(', ')
+    event.context.faqForwardedFor = forwarded
+  })
+})