feat: 完成社区首页功能迭代，新增首页聚合与工作台组件

本次提交实现了完整的社区首页功能：
1. 新增首页聚合接口与服务，包含社区统计、热门帖、活跃用户与板块数据
2. 实现帖子推荐排序、SSR缓存与点赞态同步逻辑
3. 重构导航与布局系统，新增工作台侧边栏与移动端适配
4. 优化主题色与UI样式，统一设计系统风格
5. 修复登录注册页自动跳转与组件状态同步问题

frontend/components/FooterTiming.tsx

@@ -0,0 +1,121 @@
+"use client";
+
+import { Suspense, useEffect, useRef, useState } from "react";
+import { usePathname, useSearchParams } from "next/navigation";
+
+// 版本由 Footer（RSC）从 package.json 注入；未正式设计版本号时传入空串，显示占位
+const PLACEHOLDER = "—";
+
+interface Metrics {
+  page: number; // 页面：整页加载/客户端导航总耗时
+  tpl: number; // 模板：服务端响应（SSR / RSC）耗时
+}
+
+// 硬加载：页面=loadEventEnd，模板≈TTFB（localhost 下基本等于服务端生成时间）
+function readHardNav(): Metrics {
+  const n = performance.getEntriesByType("navigation")[0] as
+    | PerformanceNavigationTiming
+    | undefined;
+  if (!n) return { page: 0, tpl: 0 };
+  return {
+    page: Math.round((n.loadEventEnd || n.domComplete || n.responseEnd) - n.startTime),
+    tpl: Math.max(0, Math.round(n.responseStart - n.requestStart)),
+  };
+}
+
+function TimingInner({ version }: { version: string }) {
+  const pathname = usePathname();
+  const search = useSearchParams().toString();
+  // 初始必须为 null：performance 仅客户端可读，直接参与首帧渲染会导致水合不一致
+  const [metrics, setMetrics] = useState<Metrics | null>(null);
+  // 记录一次站内链接点击，作为客户端导航计时起点
+  const pending = useRef<{ start: number; path: string; search: string } | null>(null);
+
+  // 挂载后读取硬加载指标；load 事件后 loadEventEnd 才有完整值，再补一次
+  useEffect(() => {
+    setMetrics(readHardNav());
+    const apply = () => setMetrics(readHardNav());
+    if (document.readyState !== "complete") {
+      window.addEventListener("load", apply, { once: true });
+      return () => window.removeEventListener("load", apply);
+    }
+  }, []);
+
+  // 捕获阶段监听站内点击（不干预任何默认行为）
+  useEffect(() => {
+    const onClick = (e: MouseEvent) => {
+      if (e.button !== 0 || e.metaKey || e.ctrlKey || e.shiftKey || e.altKey || e.defaultPrevented) return;
+      const a = (e.target as HTMLElement).closest("a");
+      if (!a || !a.href || a.target === "_blank" || a.hasAttribute("download")) return;
+      let u: URL;
+      try {
+        u = new URL(a.href);
+      } catch {
+        return;
+      }
+      if (u.origin !== location.origin) return;
+      pending.current = { start: performance.now(), path: u.pathname, search: u.search };
+    };
+    document.addEventListener("click", onClick, true);
+    return () => document.removeEventListener("click", onClick, true);
+  }, []);
+
+  // 路由切换后两帧（绘制完成）结算；模板耗时取本次 RSC fetch 的资源条目
+  useEffect(() => {
+    const p = pending.current;
+    if (!p) return;
+    if (p.path !== pathname || p.search !== (search ? `?${search}` : "")) return;
+    let raf2 = 0;
+    const raf1 = requestAnimationFrame(() => {
+      raf2 = requestAnimationFrame(() => {
+        const page = Math.round(performance.now() - p.start);
+        let tpl = 0;
+        const resources = performance.getEntriesByType("resource") as PerformanceResourceTiming[];
+        for (let i = resources.length - 1; i >= 0; i--) {
+          const r = resources[i];
+          if (
+            r.initiatorType === "fetch" &&
+            r.startTime >= p.start - 10 &&
+            r.name.startsWith(location.origin + p.path)
+          ) {
+            tpl = Math.round(r.responseEnd - r.startTime);
+            break;
+          }
+        }
+        setMetrics((prev) => ({ page: Math.max(1, page), tpl: tpl || prev?.tpl || 0 }));
+        pending.current = null;
+      });
+    });
+    return () => {
+      cancelAnimationFrame(raf1);
+      cancelAnimationFrame(raf2);
+    };
+  }, [pathname, search]);
+
+  return (
+    <span
+      className="inline-flex items-center gap-2 text-[12px] tabular-nums whitespace-nowrap"
+      style={{ color: "var(--ink-3)" }}
+    >
+      <span>版本:{version || PLACEHOLDER}</span>
+      <span aria-hidden="true">·</span>
+      <span suppressHydrationWarning>页面:{metrics ? `${metrics.page}ms` : PLACEHOLDER}</span>
+      <span aria-hidden="true">·</span>
+      <span suppressHydrationWarning>模板:{metrics ? `${metrics.tpl}ms` : PLACEHOLDER}</span>
+    </span>
+  );
+}
+
+export default function FooterTiming({ version = "" }: { version?: string }) {
+  return (
+    <Suspense
+      fallback={
+        <span className="text-[12px] meta whitespace-nowrap">
+          版本:{version || PLACEHOLDER}
+        </span>
+      }
+    >
+      <TimingInner version={version} />
+    </Suspense>
+  );
+}