feat: 类型帖互动、积分经济与发帖体验

补齐问答采纳/重开、投票匿名与有票禁编、悬赏过期退回、抽奖回帖开奖，并接入积分账本与发帖附件可见性。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/lib/postMeta.ts

@@ -0,0 +1,61 @@
+/** 帖子类型 / 可见性 / 展示文案（前后端共用约定） */
+
+export const POST_TYPES = [
+  { value: "discussion", label: "讨论", hint: "默认讨论帖" },
+  { value: "question", label: "问答", hint: "提问求解" },
+  { value: "poll", label: "投票", hint: "发起投票，读者可参与" },
+  { value: "bounty", label: "悬赏", hint: "发布时托管积分，采纳后发放" },
+  { value: "lottery", label: "抽奖", hint: "回帖即参与，截止自动开奖" },
+] as const;
+
+export type PostTypeValue = (typeof POST_TYPES)[number]["value"];
+
+export const CONTENT_ACCESS = [
+  { value: "public", label: "公开" },
+  { value: "login", label: "登录可见" },
+  { value: "reply", label: "回复可见" },
+  { value: "points", label: "积分可见" },
+] as const;
+
+export type ContentAccessValue = (typeof CONTENT_ACCESS)[number]["value"];
+
+export const BOUNTY_EXPIRE_DAYS = [3, 7, 14, 30] as const;
+export const LOTTERY_EXPIRE_DAYS = [1, 3, 7, 14] as const;
+
+export function normalizePostType(t?: string): PostTypeValue {
+  if (t === "normal" || !t) return "discussion";
+  if (POST_TYPES.some((x) => x.value === t)) return t as PostTypeValue;
+  return "discussion";
+}
+
+export function postTypeLabel(t?: string): string {
+  const n = normalizePostType(t);
+  return POST_TYPES.find((x) => x.value === n)?.label || "讨论";
+}
+
+export function contentAccessLabel(a?: string): string {
+  const hit = CONTENT_ACCESS.find((x) => x.value === a);
+  return hit?.label || "公开";
+}
+
+/** 列表 type_status → 徽章文案 */
+export function typeStatusLabel(postType?: string, typeStatus?: string): string {
+  const pt = normalizePostType(postType);
+  const s = (typeStatus || "").toLowerCase();
+  switch (pt) {
+    case "question":
+      return s === "solved" ? "已解决" : "未解决";
+    case "poll":
+      return s === "closed" ? "已结束" : "进行中";
+    case "bounty":
+      if (s === "solved") return "已采纳";
+      if (s === "expired") return "已过期";
+      return "进行中";
+    case "lottery":
+      if (s === "drawn") return "已开奖";
+      if (s === "closed") return "已截止";
+      return "进行中";
+    default:
+      return "";
+  }
+}