fix: replace require() with ES6 imports for fs and path

- Add fs and path imports at top of file
- Remove inline require() statements that violated ESLint rules
- Fixes 6 @typescript-eslint/no-var-requires errors

apps/backend/src/application/controllers/admin/csv-rates.controller.ts

@@ -40,6 +40,8 @@ import {
 import { CsvRateMapper } from '../../mappers/csv-rate.mapper';
 import { S3StorageAdapter } from '@infrastructure/storage/s3-storage.adapter';
 import { ConfigService } from '@nestjs/config';
+import * as fs from 'fs';
+import * as path from 'path';
 
 /**
  * CSV Rates Admin Controller
@@ -187,8 +189,6 @@ export class CsvRatesAdminController {
       this.logger.log(`Successfully parsed ${ratesCount} rates from ${file.filename}`);
 
       // Rename file to final name (company-name.csv)
-      const fs = require('fs');
-      const path = require('path');
       const finalPath = path.join(path.dirname(filePathToValidate), finalFilename);
 
       // Delete old file if exists
@@ -439,8 +439,6 @@ export class CsvRatesAdminController {
     this.logger.log('Fetching all CSV files (frontend compatibility)');
 
     const configs = await this.csvConfigRepository.findAll();
-    const fs = require('fs');
-    const path = require('path');
 
     // Map configs to file info format expected by frontend
     const files = configs.map((config) => {
@@ -509,8 +507,6 @@ export class CsvRatesAdminController {
     }
 
     // Delete the file from filesystem
-    const fs = require('fs');
-    const path = require('path');
     const filePath = path.join(
       process.cwd(),
       'apps/backend/src/infrastructure/storage/csv-storage/rates',