feat: 新增站点公告系统与多项体验优化

此提交完成了以下核心功能与优化：
1. 新增站点公告全流程支持：包含公告模型、CRUD接口、管理后台页面、公告详情页与首页展示
2. 实现评论楼层化与回复嵌套：重构评论系统为树状结构，支持回复评论与层级限制
3. 添加用户在线状态追踪：异步更新用户最后活跃时间并做SQL限频
4. 优化用户体验：移动端浮动操作条、统一板块标签样式、用户页签到积分展示、注册即登录优化
5. 其他细节优化：SEO站点地图新增公告页、评论分页与统计、登录/注册表单增强等

frontend/app/u/[id]/page.tsx

@@ -1,8 +1,8 @@
 import Link from "next/link";
 import { Metadata } from "next";
-import { ChevronRight, FileText, MessageCircle } from "lucide-react";
-import { fetchUserProfile, type UserProfile } from "@/lib/api";
-import UserProfileClient from "./UserProfileClient";
+import { ChevronRight, FileText, MessageCircle, Flame, AlertCircle } from "lucide-react";
+import { fetchUserProfile, fetchUserComments, type UserProfile, type UserCommentsResponse } from "@/lib/api";
+import UserProfileContent from "./UserProfileContent";
 import Avatar from "@/components/Avatar";
 
 interface UserPageProps {
@@ -25,8 +25,9 @@ export async function generateMetadata({ params }: UserPageProps): Promise<Metad
 
 export default async function UserPage({ params, searchParams }: UserPageProps) {
   const { id } = await params;
-  const { page: pageStr } = await searchParams;
-  const page = Math.max(1, parseInt(pageStr || "1", 10) || 1);
+  const sp = await searchParams;
+  const page = Math.max(1, parseInt(sp.page || "1", 10) || 1);
+  const tab: "posts" | "comments" = sp.tab === "comments" ? "comments" : "posts";
 
   let data: UserProfile;
   try {
@@ -45,11 +46,23 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
     );
   }
 
+  // 评论 tab：SSR 直出对应分页，URL（?tab=comments&page=N）与内容严格一致
+  let commentData: UserCommentsResponse | null = null;
+  let commentError = false;
+  if (tab === "comments") {
+    try {
+      commentData = await fetchUserComments(id, page);
+    } catch {
+      commentError = true;
+    }
+  }
+
   const u = data.user;
   const stats = [
     { label: "发帖", value: data.stats.post_count, icon: <FileText size={15} /> },
     { label: "评论", value: data.stats.comment_count, icon: <MessageCircle size={15} /> },
   ];
+  const showPoints = data.stats.points > 0;
 
   return (
     <div className="max-w-4xl mx-auto">
@@ -70,8 +83,7 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
           <Avatar
             name={u.nickname || u.username}
             src={u.avatar || undefined}
-            size={80}
-            className="sm:!w-[88px] sm:!h-[88px]"
+            size={88}
           />
           <div className="flex-1 min-w-0">
             <div className="flex items-center gap-2.5 flex-wrap">
@@ -90,7 +102,7 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
             <p className="meta mt-1.5 text-[13px]">
               @{u.username} · {new Date(u.created_at).toLocaleDateString("zh-CN")} 加入
             </p>
-            <div className="flex gap-2.5 mt-4">
+            <div className="flex gap-2.5 mt-4 flex-wrap">
               {stats.map((s) => (
                 <span
                   key={s.label}
@@ -98,16 +110,34 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
                   style={{ background: "var(--panel-2)", color: "var(--ink-2)" }}
                 >
                   <span style={{ color: "var(--accent)" }}>{s.icon}</span>
-                  {s.value} {s.label}
+                  <span className="tabular-nums">{s.value}</span> {s.label}
                 </span>
               ))}
+              {showPoints && (
+                <span
+                  className="inline-flex items-center gap-2 px-3.5 py-2 rounded-full text-[13px] font-semibold"
+                  style={{ background: "var(--gold-soft)", color: "var(--gold)" }}
+                  title={`连续签到 ${data.stats.streak} 天`}
+                >
+                  <Flame size={15} />
+                  <span className="tabular-nums">{data.stats.points}</span> 积分
+                  {data.stats.streak > 0 && <span className="font-normal opacity-80">· 连签 {data.stats.streak} 天</span>}
+                </span>
+              )}
             </div>
           </div>
         </div>
       </section>
 
-      {/* 发帖 / 评论 切换 */}
-      <UserProfileClient userId={id} initialPosts={data} initialPage={page} />
+      {/* 发帖 / 评论 切换（URL 驱动，SSR 直出） */}
+      <UserProfileContent
+        userId={id}
+        profile={data}
+        tab={tab}
+        commentData={commentData}
+        commentError={commentError}
+        page={page}
+      />
     </div>
   );
 }