Revert "fix: resolve all ESLint errors in backend and frontend"

This reverts commit 07dfd7e840.

paperless-backend/src/kontonummern/kontonummern.service.ts

@@ -1,4 +1,4 @@
-import { Injectable } from '@nestjs/common';
+import { Injectable, NotFoundException } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import { Kontonummer } from '../database/entities';