perf(zxdb): server-render index pages with ISR and initial data

Why
- Reduce time-to-first-content on ZXDB index pages by eliminating the initial client-side fetch and enabling incremental static regeneration.

What
- Main Explorer (/zxdb):
  - Server-renders first page of results and lookup lists (genres, languages, machinetypes) and passes them as initial props.
  - Keeps client interactivity for subsequent searches/filters.
- Labels index (/zxdb/labels):
  - Server-renders first page of empty search and passes as initial props to skip the first fetch.
- Category lists:
  - Genres (/zxdb/genres), Languages (/zxdb/languages), Machine Types (/zxdb/machinetypes) now server-render their lists and export revalidate=3600.
  - Refactored list components to accept server-provided items; removed on-mount fetching.
- Links & prefetch:
  - Replaced remaining anchors with Next Link to enable prefetch where applicable.

Tech details
- Added revalidate=3600 to the index pages for ISR.
- Updated ZxdbExplorer to accept initial results and initial filter lists; skips first client fetch when initial props are present.
- Updated LabelsSearch to accept initial payload and skip first fetch in default state.
- Updated GenreList, LanguageList, MachineTypeList to be presentational components receiving items from server pages.

Notes
- Low-churn list APIs already emit Cache-Control for CDN; list pages now render instantly from server.
- Further polish (breadcrumbs, facet counts UI) can build on this foundation without reintroducing initial network waits.

Signed-off-by: Junie@lucy.xalior.com

src/app/zxdb/ZxdbExplorer.tsx

@@ -18,14 +18,24 @@ type Paged<T> = {
   total: number;
 };
 
-export default function ZxdbExplorer() {
+export default function ZxdbExplorer({
+  initial,
+  initialGenres,
+  initialLanguages,
+  initialMachines,
+}: {
+  initial?: Paged<Item>;
+  initialGenres?: { id: number; name: string }[];
+  initialLanguages?: { id: string; name: string }[];
+  initialMachines?: { id: number; name: string }[];
+}) {
   const [q, setQ] = useState("");
   const [page, setPage] = useState(1);
   const [loading, setLoading] = useState(false);
-  const [data, setData] = useState<Paged<Item> | null>(null);
-  const [genres, setGenres] = useState<{ id: number; name: string }[]>([]);
-  const [languages, setLanguages] = useState<{ id: string; name: string }[]>([]);
-  const [machines, setMachines] = useState<{ id: number; name: string }[]>([]);
+  const [data, setData] = useState<Paged<Item> | null>(initial ?? null);
+  const [genres, setGenres] = useState<{ id: number; name: string }[]>(initialGenres ?? []);
+  const [languages, setLanguages] = useState<{ id: string; name: string }[]>(initialLanguages ?? []);
+  const [machines, setMachines] = useState<{ id: number; name: string }[]>(initialMachines ?? []);
   const [genreId, setGenreId] = useState<number | "">("");
   const [languageId, setLanguageId] = useState<string | "">("");
   const [machinetypeId, setMachinetypeId] = useState<number | "">("");
@@ -59,18 +69,23 @@ export default function ZxdbExplorer() {
   }
 
   useEffect(() => {
+    // Avoid immediate client fetch on first paint if server provided initial data
+    if (initial && page === 1 && q === "" && genreId === "" && languageId === "" && machinetypeId === "" && sort === "title") {
+      return;
+    }
     fetchData(q, page);
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [page, genreId, languageId, machinetypeId, sort]);
 
-  // Load filter lists once
+  // Load filter lists on mount only if not provided by server
   useEffect(() => {
+    if (initialGenres && initialLanguages && initialMachines) return;
     async function loadLists() {
       try {
         const [g, l, m] = await Promise.all([
-          fetch("/api/zxdb/genres", { cache: "no-store" }).then((r) => r.json()),
-          fetch("/api/zxdb/languages", { cache: "no-store" }).then((r) => r.json()),
-          fetch("/api/zxdb/machinetypes", { cache: "no-store" }).then((r) => r.json()),
+          fetch("/api/zxdb/genres", { cache: "force-cache" }).then((r) => r.json()),
+          fetch("/api/zxdb/languages", { cache: "force-cache" }).then((r) => r.json()),
+          fetch("/api/zxdb/machinetypes", { cache: "force-cache" }).then((r) => r.json()),
         ]);
         setGenres(g.items ?? []);
         setLanguages(l.items ?? []);
@@ -78,7 +93,7 @@ export default function ZxdbExplorer() {
       } catch {}
     }
     loadLists();
-  }, []);
+  }, [initialGenres, initialLanguages, initialMachines]);
 
   function onSubmit(e: React.FormEvent) {
     e.preventDefault();