feat(ui): enhance dark mode styling support

- AppSwitcher: add dark mode backgrounds, borders and hover effects
- ConfirmDialog: apply dark theme colors to dialog elements
- ProviderList: update list items and buttons for dark mode
- Global styles: use color-scheme property for native controls theming

Ensures all interactive components have proper visual feedback and consistent UX in dark mode.

src/index.css

@@ -12,12 +12,17 @@
 html {
   @apply font-sans antialiased;
   line-height: 1.5;
+  /* 让原生控件与滚动条随主题切换配色 */
+  color-scheme: light;
 }
 
 body {
   @apply m-0 p-0 bg-gray-50 text-gray-900 text-sm dark:bg-gray-950 dark:text-gray-100;
 }
 
+/* 暗色模式下启用暗色原生控件/滚动条配色 */
+html.dark { color-scheme: dark; }
+
 /* 滚动条样式 */
 ::-webkit-scrollbar {
   @apply w-1.5 h-1.5;