升级帖子编辑与 Feed 体验：TipTap 富文本、修订历史、排序与编辑时限。

将 Markdown 编辑器替换为 TipTap WYSIWYG，新增帖子修订记录与 diff 展示；首页支持最新/回复排序与本地缓存；后台可配置编辑时限与锁定帖子；侧边栏整合板块导航并优化 Feed 布局。

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

frontend/package.json

@@ -17,10 +17,19 @@
     "@radix-ui/react-slot": "^1.2.5",
     "@radix-ui/react-switch": "^1.3.0",
     "@tanstack/react-virtual": "^3.11.2",
+    "@tiptap/core": "^3.26.1",
+    "@tiptap/extension-image": "^3.26.1",
+    "@tiptap/extension-link": "^3.26.1",
+    "@tiptap/extension-placeholder": "^3.26.1",
+    "@tiptap/extension-underline": "^3.26.1",
+    "@tiptap/pm": "^3.26.1",
+    "@tiptap/react": "^3.26.1",
+    "@tiptap/starter-kit": "^3.26.1",
     "autoprefixer": "^10.5.0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "dayjs": "^1.11.13",
+    "diff": "^9.0.0",
     "dompurify": "^3.4.10",
     "lucide-react": "^1.18.0",
     "marked": "^18.0.5",