feat: 改进设置页面UI和国际化支持 / Improve settings pages UI and i18n support

- 添加 rehype-raw 依赖以支持在 markdown 中渲染 HTML
  Add rehype-raw dependency to support HTML rendering in markdown

- 重构 memory-settings-page，提取 formatMemorySection 函数减少重复代码
  Refactor memory-settings-page by extracting formatMemorySection function to reduce code duplication

- 改进空状态显示，使用 HTML span 标签替代 markdown 斜体，提供更好的样式控制
  Improve empty state display by using HTML span tags instead of markdown italics for better style control

- 为 skill-settings-page 添加完整的国际化支持，替换硬编码的英文文本
  Add complete i18n support for skill-settings-page, replacing hardcoded English text

- 更新国际化文件，添加技能设置页面的空状态文本（中英文）
  Update i18n files with empty state text for skill settings page (both Chinese and English)

- 在 streamdown 插件配置中添加 rehypeRaw 以支持 HTML 渲染
  Add rehypeRaw to streamdown plugins configuration to support HTML rendering

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

frontend/src/core/i18n/locales/en-US.ts

@@ -243,7 +243,7 @@ export const enUS: Translations = {
         longTermBackground: "Long-term background",
         updatedAt: "Updated at",
         facts: "Facts",
-        empty: "Empty",
+        empty: "empty",
         table: {
           category: "Category",
           confidence: "Confidence",
@@ -282,6 +282,10 @@ export const enUS: Translations = {
       description:
         "Manage the configuration and enabled status of the agent skills.",
       createSkill: "Create skill",
+      emptyTitle: "No agent skill yet",
+      emptyDescription:
+        "Put your agent skill folders under the `/skills/custom` folder under the root folder of DeerFlow.",
+      emptyButton: "Create Your First Skill",
     },
     notification: {
       title: "Notification",