Add visual progress indicator for AI assignment batches

- Add AssignmentJob model to track AI assignment progress
- Create startAIAssignmentJob mutation for background processing
- Add getAIAssignmentJobStatus query for polling progress
- Update AI assignment service with progress callback support
- Add progress bar UI showing batch/project processing status
- Add toast notifications for job completion/failure
- Add AI_SUGGESTIONS_READY notification type

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/server/services/in-app-notification.ts

@@ -16,6 +16,7 @@ export const NotificationTypes = {
   // Admin notifications
   FILTERING_COMPLETE: 'FILTERING_COMPLETE',
   FILTERING_FAILED: 'FILTERING_FAILED',
+  AI_SUGGESTIONS_READY: 'AI_SUGGESTIONS_READY',
   NEW_APPLICATION: 'NEW_APPLICATION',
   BULK_APPLICATIONS: 'BULK_APPLICATIONS',
   DOCUMENTS_UPLOADED: 'DOCUMENTS_UPLOADED',