feat(admin): 独立后台壳、站点分析与聊天监管，公开站拆出主题切换与访问埋点

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

frontend/components/ThemeToggle.tsx

@@ -0,0 +1,79 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { usePathname } from "next/navigation";
+import { Moon, Sun } from "lucide-react";
+
+type Theme = "light" | "dark";
+
+function readThemeCookie(): Theme {
+  if (typeof document === "undefined") return "light";
+  return document.cookie.match(/(?:^|;\s*)j13-theme=dark/) ? "dark" : "light";
+}
+
+function applyTheme(theme: Theme) {
+  document.documentElement.classList.toggle("dark", theme === "dark");
+  document.cookie = `j13-theme=${theme}; path=/; max-age=31536000`;
+}
+
+/**
+ * 明暗主题切换：cookie 为真相源；公开顶栏与后台顶栏共用。
+ * 首屏严格用 initialTheme，挂载后再按 cookie 校正，避免 hydration 不一致。
+ */
+export default function ThemeToggle({
+  initialTheme = "light",
+  className,
+  style,
+  /** icon = 仅图标按钮；labeled = 带「浅色/深色模式」文案（移动抽屉用） */
+  labelMode = "icon",
+  iconSize = 17,
+}: {
+  initialTheme?: Theme;
+  className?: string;
+  style?: React.CSSProperties;
+  labelMode?: "icon" | "labeled";
+  iconSize?: number;
+}) {
+  const pathname = usePathname();
+  const [theme, setTheme] = useState<Theme>(initialTheme);
+  const [ready, setReady] = useState(false);
+
+  useEffect(() => {
+    const saved = readThemeCookie();
+    document.documentElement.classList.toggle("dark", saved === "dark");
+    setTheme(saved);
+    setReady(true);
+  }, [pathname]);
+
+  const toggle = () => {
+    const next: Theme = theme === "dark" ? "light" : "dark";
+    setTheme(next);
+    applyTheme(next);
+  };
+
+  // 未挂载完成前始终展示 SSR 初值，保证与服务端 HTML 一致
+  const shown = ready ? theme : initialTheme;
+
+  if (labelMode === "labeled") {
+    return (
+      <button type="button" onClick={toggle} className={className} style={style}>
+        {shown === "dark" ? <Sun size={iconSize} /> : <Moon size={iconSize} />}
+        {shown === "dark" ? "浅色模式" : "深色模式"}
+      </button>
+    );
+  }
+
+  return (
+    <button
+      type="button"
+      onClick={toggle}
+      className={className}
+      style={style}
+      aria-label="切换主题"
+      data-tip={shown === "dark" ? "切换浅色" : "切换深色"}
+      suppressHydrationWarning
+    >
+      {shown === "dark" ? <Sun size={iconSize} /> : <Moon size={iconSize} />}
+    </button>
+  );
+}