支持公开用户主页、帖子图缩略图与编辑器图组排版。

新增用户签名与活动统计、图片灯箱；正文按需生成缩略图；TipTap 支持多图分组与环绕排版，并注入站点标题避免刷新闪烁。

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

frontend/src/components/ImageLightbox.tsx

@@ -0,0 +1,58 @@
+import { useEffect } from 'react';
+import { X } from 'lucide-react';
+import { createPortal } from 'react-dom';
+
+interface Props {
+  src: string | null;
+  alt?: string;
+  open: boolean;
+  onClose: () => void;
+}
+
+/** 帖子正文图片灯箱：展示原图，点击遮罩 / Esc / 关闭按钮退出 */
+export default function ImageLightbox({ src, alt = '', open, onClose }: Props) {
+  useEffect(() => {
+    if (!open) return;
+    const onKey = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') onClose();
+    };
+    const prev = document.body.style.overflow;
+    document.body.style.overflow = 'hidden';
+    window.addEventListener('keydown', onKey);
+    return () => {
+      document.body.style.overflow = prev;
+      window.removeEventListener('keydown', onKey);
+    };
+  }, [open, onClose]);
+
+  if (!open || !src) return null;
+
+  return createPortal(
+    <div className="image-lightbox" role="dialog" aria-modal="true" aria-label="查看原图">
+      <button
+        type="button"
+        className="image-lightbox-backdrop"
+        aria-label="关闭"
+        onClick={onClose}
+      />
+      <button
+        type="button"
+        className="image-lightbox-close"
+        aria-label="关闭"
+        onClick={onClose}
+      >
+        <X size={20} aria-hidden />
+      </button>
+      <div className="image-lightbox-stage">
+        <img
+          src={src}
+          alt={alt || '原图'}
+          className="image-lightbox-img"
+          decoding="async"
+        />
+      </div>
+      <p className="image-lightbox-hint">点击空白处关闭</p>
+    </div>,
+    document.body,
+  );
+}