feat: opt-in Journal search page and JournalSearchBox

- journal.routes.search (off by default) registers journal-search, the
  results page for ?q= in the API's relevance order (no sort is sent),
  server-rendered with a Polish-aware result count.
- JournalSearchBox: an icon button and a WAI-ARIA combobox with debounced
  ?fields=suggest suggestions, stale answers dropped, query words marked
  ignoring diacritics; a plain GET form without JS.
- The module keeps the search path out of the route cache and the sitemap
  and marks it noindex, follow.
- Client: suggestPosts and the fields option; useJournalLinks.searchLink.

app/utils/types.ts

@@ -49,6 +49,19 @@ export interface JournalPost {
   updated_at: string | null
 }
 
+/**
+ * One row of GET /posts?fields=suggest: a subset of JournalPost for a search
+ * box. `excerpt` is plain text of about 160 characters.
+ */
+export interface JournalPostSuggestion {
+  id: number
+  title: string
+  slug: string
+  excerpt: string
+  featured_image_url: string | null
+  published_at: string | null
+}
+
 /** previous_post / next_post on GET /posts/{slug}. */
 export interface JournalPostSibling {
   id: number
@@ -121,6 +134,8 @@ export interface JournalRoutes {
   category: string | false
   tag: string | false
   author: string | false
+  /** Search results page; the term is the `q` query parameter. Off by default. */
+  search: string | false
 }
 
 export interface JournalPerPage {
@@ -128,6 +143,7 @@ export interface JournalPerPage {
   category: number
   tag: number
   author: number
+  search: number
 }
 
 /** Options of the `journal` config key in nuxt.config. */