feat: align frontend languages with posts api

src/components/messageStream/hooks/useGroupedByDay.test.ts

@@ -8,7 +8,7 @@ function makePost(id: string, isoDate: string): Post {
     id,
     categoryId: 1,
     categorySlug: "x",
-    language: "zh-CN",
+    language: "zh",
     attachments: [],
     isRecommended: false,
     publishedAt: isoDate,
@@ -25,7 +25,7 @@ describe("useGroupedByDay", () => {
       makePost("c", "2026-02-28T01:00:00.000Z"),
       makePost("d", "2026-05-16T12:00:00.000Z"),
     ];
-    const { result } = renderHook(() => useGroupedByDay(posts, "zh-CN"));
+    const { result } = renderHook(() => useGroupedByDay(posts, "zh"));
     expect(result.current.length).toBeGreaterThanOrEqual(2);
     const allIds = result.current.flatMap((g) => g.items.map((p) => p.id));
     expect(allIds).toEqual(["a", "b", "c", "d"]);
@@ -47,7 +47,7 @@ describe("useGroupedByDay", () => {
   });
 
   it("returns empty array for empty input", () => {
-    const { result } = renderHook(() => useGroupedByDay([], "zh-CN"));
+    const { result } = renderHook(() => useGroupedByDay([], "zh"));
     expect(result.current).toEqual([]);
   });
 });

src/components/messageStream/hooks/useGroupedByDay.ts

@@ -8,9 +8,16 @@ export type DayGroup = {
 };
 
 function localeFor(lang: string): string {
-  if (lang === "zh-TW") return "zh-TW";
-  if (lang === "zh-CN") return "zh-CN";
-  return "en-US";
+  const locales: Record<string, string> = {
+    zh: "zh-CN",
+    en: "en-US",
+    ja: "ja-JP",
+    ko: "ko-KR",
+    vi: "vi-VN",
+    id: "id-ID",
+    ms: "ms-MY",
+  };
+  return locales[lang] ?? "en-US";
 }
 
 function dayKey(iso: string): string {
@@ -28,12 +35,10 @@ function dayLabel(iso: string, lang: string): string {
     a.getMonth() === b.getMonth() &&
     a.getDate() === b.getDate();
   if (isSameDay(d, today)) {
-    if (lang === "en") return "Today";
-    return "今天";
+    return lang === "zh" ? "今天" : "Today";
   }
   if (isSameDay(d, yesterday)) {
-    if (lang === "en") return "Yesterday";
-    return "昨天";
+    return lang === "zh" ? "昨天" : "Yesterday";
   }
   return new Intl.DateTimeFormat(localeFor(lang), {
     month: "long",

src/components/messageStream/hooks/usePostStream.ts

@@ -35,6 +35,7 @@ function postMatchesType(post: Post, type: string): boolean {
       return a.kind === "image" || a.mime.startsWith("image/");
     if (type === "video")
       return a.kind === "video" || a.mime.startsWith("video/");
+    if (type === "music") return a.mime.startsWith("audio/") || ext === "mp3";
     if (type === "pdf") return ext === "pdf" || a.mime === "application/pdf";
     if (type === "ppt")
       return (