完善 TipTap 编辑器与个人资料页：头像裁剪、Tab 缩进、文章内链、Markdown 工具与 Tooltip，并更新样式与 Feed 缓存。

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

frontend/src/utils/avatarCrop.ts

@@ -0,0 +1,66 @@
+import type { Area } from 'react-easy-crop';
+
+export const AVATAR_ACCEPT = 'image/jpeg,image/png,image/gif,image/webp';
+export const AVATAR_MIME_TYPES = ['image/jpeg', 'image/png', 'image/gif', 'image/webp'];
+
+/** 头像输出尺寸 */
+export const AVATAR_OUTPUT_SIZE = 512;
+
+function loadImage(src: string): Promise<HTMLImageElement> {
+  return new Promise((resolve, reject) => {
+    const img = new Image();
+    img.onload = () => resolve(img);
+    img.onerror = () => reject(new Error('图片加载失败'));
+    img.src = src;
+  });
+}
+
+/** 校验头像文件，返回错误信息或 null */
+export function validateAvatarFile(file: File, maxMb: number): string | null {
+  if (!AVATAR_MIME_TYPES.includes(file.type)) {
+    return '仅支持 JPG、PNG、GIF、WebP 格式';
+  }
+  if (file.size > maxMb * 1024 * 1024) {
+    return `头像不能超过 ${maxMb}MB`;
+  }
+  return null;
+}
+
+/** 将裁剪区域渲染为 JPEG 文件 */
+export async function getCroppedAvatarFile(
+  imageSrc: string,
+  pixelCrop: Area,
+  originalName = 'avatar.jpg',
+): Promise<File> {
+  const image = await loadImage(imageSrc);
+  const canvas = document.createElement('canvas');
+  const size = AVATAR_OUTPUT_SIZE;
+  canvas.width = size;
+  canvas.height = size;
+
+  const ctx = canvas.getContext('2d');
+  if (!ctx) throw new Error('裁剪失败');
+
+  ctx.drawImage(
+    image,
+    pixelCrop.x,
+    pixelCrop.y,
+    pixelCrop.width,
+    pixelCrop.height,
+    0,
+    0,
+    size,
+    size,
+  );
+
+  const blob = await new Promise<Blob>((resolve, reject) => {
+    canvas.toBlob(
+      b => (b ? resolve(b) : reject(new Error('裁剪失败'))),
+      'image/jpeg',
+      0.92,
+    );
+  });
+
+  const baseName = originalName.replace(/\.[^.]+$/, '') || 'avatar';
+  return new File([blob], `${baseName}.jpg`, { type: 'image/jpeg' });
+}