i18n: translate all public page bodies (EN + IT)

Internationalised the ~44 public pages with next-intl (the shell was
already translated). Each page now pulls its copy from a "pages.<slug>"
namespace via getTranslations (server) / useTranslations (client); the
EN + IT catalogs were authored by parallel agents and merged centrally,
with natural Italian (ICU plurals) and it backfilled from en for any
gap. request.ts gained getMessageFallback/onError so a missing key
degrades to the English value, never a raw key.

Behaviour unchanged (only display text moved to t() calls; queries,
actions, fields, ContentCard structure preserved). Verified on the prod
server: with NEXT_LOCALE=it, home/community/staff/news/shop/rankings all
render Italian copy, no raw-key leakage; English unchanged. The nav
language switcher toggles EN/IT live. tsc 0, vitest 49/49, next build 0.

Admin pages intentionally left in English (staff tooling).

src/app/leaderboard/page.tsx

@@ -1,3 +1,4 @@
+import { getTranslations } from "next-intl/server";
 import Link from "next/link";
 import { ContentCard, EmptyState, RankBadge } from "@/components/public/ui";
 import { avatarImageUrl } from "@/lib/format";
@@ -71,6 +72,7 @@ export default async function LeaderboardPage({
 }: {
   searchParams: Promise<{ type?: string }>;
 }) {
+  const t = await getTranslations("pages.leaderboard");
   const { type } = await searchParams;
   const active: TabKey = TABS.some((t) => t.key === type) ? (type as TabKey) : "credits";
   const activeTab = TABS.find((t) => t.key === active)!;
@@ -86,33 +88,33 @@ export default async function LeaderboardPage({
     <main style={{ display: "grid", gap: "1.5rem" }}>
       <ContentCard
         icon="📊"
-        title="Leaderboard"
-        subtitle={`Top 20 players by ${activeTab.label.toLowerCase()}`}
+        title={t("title")}
+        subtitle={t("subtitle", { currency: t(`tab_${active}`).toLowerCase() })}
       />
 
       <div className="nav" style={{ gap: "0.5rem" }}>
-        {TABS.map((t) => (
+        {TABS.map((t2) => (
           <Link
-            key={t.key}
-            href={`/leaderboard?type=${t.key}`}
-            className={`btn ${t.key === active ? "btn-primary" : "btn-outline"}`}
+            key={t2.key}
+            href={`/leaderboard?type=${t2.key}`}
+            className={`btn ${t2.key === active ? "btn-primary" : "btn-outline"}`}
           >
-            {t.label}
+            {t(`tab_${t2.key}`)}
           </Link>
         ))}
       </div>
 
       <ContentCard padded={rows.length === 0}>
         {rows.length === 0 ? (
-          <EmptyState icon="📊">No rankings to show yet.</EmptyState>
+          <EmptyState icon="📊">{t("emptyState")}</EmptyState>
         ) : (
           <table>
             <thead>
               <tr>
                 <th style={{ width: "3rem" }}>#</th>
-                <th style={{ width: "3.5rem" }}>Avatar</th>
-                <th>Player</th>
-                <th style={{ textAlign: "right" }}>{activeTab.label}</th>
+                <th style={{ width: "3.5rem" }}>{t("colAvatar")}</th>
+                <th>{t("colPlayer")}</th>
+                <th style={{ textAlign: "right" }}>{t(`tab_${active}`)}</th>
               </tr>
             </thead>
             <tbody>