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/labels/LabelsSearch.tsx

@@ -1,16 +1,17 @@
 "use client";
 
-import { useEffect, useMemo, useState } from "react";
+import { useEffect, useMemo, useRef, useState } from "react";
 import Link from "next/link";
 
 type Label = { id: number; name: string; labeltypeId: string | null };
 type Paged<T> = { items: T[]; page: number; pageSize: number; total: number };
 
-export default function LabelsSearch() {
+export default function LabelsSearch({ initial }: { initial?: Paged<Label> }) {
   const [q, setQ] = useState("");
   const [page, setPage] = useState(1);
-  const [data, setData] = useState<Paged<Label> | null>(null);
+  const [data, setData] = useState<Paged<Label> | null>(initial ?? null);
   const [loading, setLoading] = useState(false);
+  const firstLoadSkipped = useRef(false);
   const pageSize = 20;
   const totalPages = useMemo(() => (data ? Math.max(1, Math.ceil(data.total / data.pageSize)) : 1), [data]);
 
@@ -32,6 +33,11 @@ export default function LabelsSearch() {
   }
 
   useEffect(() => {
+    // If server provided initial data for first page of empty search, skip first fetch
+    if (!firstLoadSkipped.current && initial && !q && page === 1) {
+      firstLoadSkipped.current = true;
+      return;
+    }
     load();
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [page]);