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/guilds/[id]/forum/new/page.tsx

@@ -1,3 +1,4 @@
+import { getTranslations } from "next-intl/server";
 import Link from "next/link";
 import { notFound, redirect } from "next/navigation";
 import { ContentCard } from "@/components/public/ui";
@@ -12,6 +13,7 @@ export default async function NewThreadPage({
 }: {
   params: Promise<{ id: string }>;
 }) {
+  const t = await getTranslations("pages.guildForumNew");
   const { id } = await params;
   const guildId = Number(id);
   if (!Number.isInteger(guildId) || guildId <= 0) notFound();
@@ -36,13 +38,13 @@ export default async function NewThreadPage({
   return (
     <main style={{ display: "grid", gap: "1.5rem" }}>
       <p style={{ margin: 0 }}>
-        <Link href={`/guilds/${guild.id}/forum`}>← Back to forum</Link>
+        <Link href={`/guilds/${guild.id}/forum`}>{t("backToForum")}</Link>
       </p>
 
       <ContentCard
         icon="✍️"
-        title="New thread"
-        subtitle={`in ${guild.name || "Unnamed guild"} forum`}
+        title={t("title")}
+        subtitle={t("subtitle", { guild: guild.name || t("unnamedGuild") })}
       >
         <form action={postThread}>
           {/* Guild target drives the write; the author is taken from the session
@@ -50,35 +52,35 @@ export default async function NewThreadPage({
           <input type="hidden" name="guildId" value={String(guild.id)} />
 
           <label htmlFor="thread-subject" className="muted">
-            Subject
+            {t("subjectLabel")}
           </label>
           <input
             id="thread-subject"
             name="subject"
             required
             maxLength={255}
-            placeholder="Thread subject"
+            placeholder={t("subjectPlaceholder")}
             style={{ width: "100%", margin: "0.4rem 0 0.9rem" }}
           />
 
           <label htmlFor="thread-message" className="muted">
-            Message
+            {t("messageLabel")}
           </label>
           <textarea
             id="thread-message"
             name="message"
             required
             rows={8}
-            placeholder="Write your opening post…"
+            placeholder={t("messagePlaceholder")}
             style={{ width: "100%", margin: "0.4rem 0 1rem", resize: "vertical" }}
           />
 
           <div style={{ display: "flex", gap: "0.5rem", alignItems: "center" }}>
             <button type="submit" className="btn btn-primary">
-              Post thread
+              {t("postThread")}
             </button>
             <Link href={`/guilds/${guild.id}/forum`} className="btn btn-outline">
-              Cancel
+              {t("cancel")}
             </Link>
           </div>
         </form>