feat: add export validation results to Excel feature

Add export functionality to CleanerPage that allows users to export
the currently displayed validation results to an Excel file.

- Add ExportResultItem and ExportResultResponse types
- Create ResultExporter service using ExcelJS
- Register cleaner:exportResults IPC handler
- Add exportResults method to preload API
- Connect export button in CleanerPage to export handler

Export features:
- Exports filtered results (respecting manager/visibility filters)
- Includes selection status column
- Saves to app data directory/exports/校验结果.xlsx

Co-Authored-By: Claude (glm-5) <noreply@anthropic.com>

src/shared/ipc-channels.ts

@@ -15,6 +15,7 @@ export const IPC_CHANNELS = {
 
   // Cleaner service
   CLEANER_RUN: 'cleaner:run',
+  CLEANER_EXPORT_RESULTS: 'cleaner:exportResults',
 
   // Database service - MySQL
   DATABASE_MYSQL_CONNECT: 'database:mysql:connect',