Support custom WebUI fonts and UI additions

Backend: add CheckWebUIFontExist API and route; set --font-family-mono CSS variable in InitWebUi for aacute/custom/default. Improve webui font uploader: force saved filename to CustomFont, robustly clean old webui/CustomFont files, and log failures.

Frontend: add FileManager.checkWebUIFontExists; update theme settings to show upload UI only when 'custom' is selected, display uploaded status, attempt delete-before-upload, reload after actions, and adjust Accordion props. ColorPicker: enable pointer events on PopoverContent to allow dragging. applyFont now sets --font-family-mono for all modes.

packages/napcat-webui-frontend/src/controllers/file_manager.ts

@@ -218,4 +218,11 @@ export default class FileManager {
     );
     return data.data;
   }
+
+  public static async checkWebUIFontExists () {
+    const { data } = await serverRequest.get<ServerResponse<boolean>>(
+      '/File/font/exists/webui'
+    );
+    return data.data;
+  }
 }