feat(compose): 正文内嵌隐藏块并升级 Markdown 编辑器

去掉整帖可见性表单，改为 :::hide 按块脱敏；工具栏补齐代码块、链接/图片对话框与粘贴拖拽上传。

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

frontend/lib/api.ts

@@ -792,8 +792,6 @@ export async function apiCreatePost(data: {
   content: string;
   tags?: string;
   post_type?: string;
-  content_access?: string;
-  access_points?: number;
   type_meta?: string;
   attachment_ids?: number[];
 }) {
@@ -820,8 +818,6 @@ export async function apiUpdatePost(
     title?: string;
     content?: string;
     tags?: string;
-    content_access?: string;
-    access_points?: number;
     type_meta?: string;
     attachment_ids?: number[];
   }