feat: 用自定义侧边栏替换聊天室 Conversations 组件，提取公共 SidebarGroup 和 date-group

tests/web/features/inbox/MaterialCard.test.tsx

@@ -18,7 +18,7 @@ const MOCK_MATERIAL: Material = {
 };
 
 describe("MaterialCard", () => {
-  test("渲染素材描述、时间和状态标签", () => {
+  test("渲染素材描述和状态标签", () => {
     renderWithProviders(
       createElement(MaterialCard, {
         material: MOCK_MATERIAL,
@@ -28,7 +28,6 @@ describe("MaterialCard", () => {
       }),
     );
     expect(screen.getByText("测试素材描述")).not.toBeNull();
-    expect(screen.getByText("今天")).not.toBeNull();
     expect(screen.getByText("待审核")).not.toBeNull();
   });