feat: add localization and site settings

src/i18n/getLocale.ts

@@ -0,0 +1,30 @@
+import { cookies, headers } from "next/headers";
+import { DEFAULT_LOCALE, LOCALES, LOCALE_COOKIE, type Locale } from "./messages";
+
+function isLocale(v: string | undefined | null): v is Locale {
+  return !!v && (LOCALES as string[]).includes(v);
+}
+
+/**
+ * Resolve the current locale on the server.
+ *  1. Explicit cookie
+ *  2. Accept-Language header (en* → en, otherwise zh)
+ *  3. Default
+ */
+export async function getServerLocale(): Promise<Locale> {
+  const cookieStore = await cookies();
+  const cookieLocale = cookieStore.get(LOCALE_COOKIE)?.value;
+  if (isLocale(cookieLocale)) return cookieLocale;
+
+  try {
+    const h = await headers();
+    const accept = h.get("accept-language") || "";
+    const first = accept.split(",")[0]?.trim().toLowerCase() || "";
+    if (first.startsWith("en")) return "en";
+    if (first.startsWith("zh")) return "zh";
+  } catch {
+    // headers() can throw outside request scope
+  }
+
+  return DEFAULT_LOCALE;
+}