fix: update Blob creation for file uploads to handle buffer offsets correctly

backend/src/ai/ai.controller.ts

@@ -1,7 +1,8 @@
 import { Controller, Get } from '@nestjs/common';
 import { Public } from '../auth/decorators/public.decorator';
 import { AI_CATEGORIZATION_MODEL } from './ai.service';
-import { RECEIPT_IMPORT_MODEL } from '../receipt-import/receipt-import.service';
+
+const RECEIPT_IMPORT_MODEL = 'mistral-small-2603';
 
 export interface AiModelInfo {
   id: string;