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/points.ts

@@ -0,0 +1,14 @@
+/** 积分流水原因文案 */
+const REASON_LABELS: Record<string, string> = {
+  checkin: "每日签到",
+  unlock_post: "解锁正文",
+  download_file: "附件下载",
+  migrate_checkin: "历史签到回填",
+  bounty_escrow: "悬赏托管",
+  bounty_refund: "悬赏退回",
+  bounty_award: "悬赏采纳",
+};
+
+export function pointReasonLabel(reason: string): string {
+  return REASON_LABELS[reason] || reason || "其他";
+}