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/components/home/WorkspaceNav.tsx

@@ -14,7 +14,11 @@ function boardHref(id: number) {
 export function WorkspaceNav({ boards, user }: { boards: BoardWithCount[]; user: User | null }) {
   const params = useSearchParams();
   const activeBoard = Number(params.get("board")) || 0;
-  const composeHref = user ? "/compose" : "/login?redirect=/compose";
+  const composePath =
+    activeBoard > 0 ? `/compose?board=${activeBoard}` : "/compose";
+  const composeHref = user
+    ? composePath
+    : `/login?redirect=${encodeURIComponent(composePath)}`;
 
   return (
     <nav className="hidden lg:block w-56 xl:w-60 shrink-0" aria-label="工作台导航">
@@ -96,7 +100,11 @@ export function WorkspaceNavMobile({
 }) {
   const params = useSearchParams();
   const activeBoard = Number(params.get("board")) || 0;
-  const composeHref = user ? "/compose" : "/login?redirect=/compose";
+  const composePath =
+    activeBoard > 0 ? `/compose?board=${activeBoard}` : "/compose";
+  const composeHref = user
+    ? composePath
+    : `/login?redirect=${encodeURIComponent(composePath)}`;
 
   return (
     <div className="lg:hidden -mx-4 sm:-mx-6 px-4 sm:px-6">