fix: convert all test files from jest to vitest and fix QBittorrentClient import

- Convert RTorrentClient.test.js to use vi.mock() instead of jest.mock()
- Convert QBittorrentClient.test.js to use vi.mock() instead of jest.mock()
- Convert SABnzbdClient.test.js to use vi.mock() instead of jest.mock()
- Convert TransmissionClient.test.js to use vi.mock() instead of jest.mock()
- Convert downloadClients.test.js to use vi.mock() instead of jest.mock()
- Convert integration/downloadClients.test.js to use vi.mock() instead of jest.mock()
- Fix legacy qbittorrent.test.js to import QBittorrentClient from new location
- Add getRtorrentInstances mock to downloadClients.test.js
- Add RTORRENT_INSTANCES to integration test environment variables

tests/unit/clients/QBittorrentClient.test.js

@@ -1,11 +1,12 @@
 // Copyright (c) 2026 Gordon Bolton. MIT License.
 const QBittorrentClient = require('../../../server/clients/QBittorrentClient');
 const axios = require('axios');
+const { vi } = require('vitest');
 
 // Mock axios
-jest.mock('axios');
-jest.mock('../../../server/utils/logger', () => ({
-  logToFile: jest.fn()
+vi.mock('axios');
+vi.mock('../../../server/utils/logger', () => ({
+  logToFile: vi.fn()
 }));
 
 describe('QBittorrentClient', () => {
@@ -22,9 +23,9 @@ describe('QBittorrentClient', () => {
     };
     
     client = new QBittorrentClient(mockConfig);
-    
+
     // Clear all mocks
-    jest.clearAllMocks();
+    vi.clearAllMocks();
   });
 
   describe('Constructor', () => {
@@ -89,11 +90,11 @@ describe('QBittorrentClient', () => {
   describe('Connection Test', () => {
     it('should test connection successfully', async () => {
       // Mock login success
-      client.login = jest.fn().mockResolvedValue(true);
-      
+      client.login = vi.fn().mockResolvedValue(true);
+
       // Mock version request
       const mockResponse = { data: 'v4.3.5' };
-      client.makeRequest = jest.fn().mockResolvedValue(mockResponse);
+      client.makeRequest = vi.fn().mockResolvedValue(mockResponse);
       
       const result = await client.testConnection();
       
@@ -102,7 +103,7 @@ describe('QBittorrentClient', () => {
     });
 
     it('should handle connection test failure', async () => {
-      client.login = jest.fn().mockRejectedValue(new Error('Auth failed'));
+      client.login = vi.fn().mockRejectedValue(new Error('Auth failed'));
       
       const result = await client.testConnection();
       
@@ -200,15 +201,15 @@ describe('QBittorrentClient', () => {
       const authError = {
         response: { status: 403 }
       };
-      
+
       // Second login attempt succeeds
-      client.login = jest.fn()
+      client.login = vi.fn()
         .mockResolvedValueOnce(false)
         .mockResolvedValueOnce(true);
-      
+
       // Retry request succeeds
       const successResponse = { data: 'success' };
-      axios.get = jest.fn()
+      axios.get = vi.fn()
         .mockRejectedValueOnce(authError)
         .mockResolvedValueOnce(successResponse);