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/integration/downloadClients.test.js

@@ -1,10 +1,11 @@
 // Copyright (c) 2026 Gordon Bolton. MIT License.
-const { 
+const {
   initializeClients,
   getAllDownloads,
   getDownloadsByClientType,
   testAllConnections
 } = require('../../server/utils/downloadClients');
+const { vi } = require('vitest');
 
 // Mock environment variables for testing
 process.env.SABNZBD_INSTANCES = JSON.stringify([
@@ -36,10 +37,20 @@ process.env.TRANSMISSION_INSTANCES = JSON.stringify([
   }
 ]);
 
+process.env.RTORRENT_INSTANCES = JSON.stringify([
+  {
+    id: 'test-rtorrent',
+    name: 'Test rTorrent',
+    url: 'http://localhost:8080/RPC2',
+    username: 'rtorrent',
+    password: 'rtorrent'
+  }
+]);
+
 // Mock axios to prevent actual network calls
-jest.mock('axios');
-jest.mock('../../server/utils/logger', () => ({
-  logToFile: jest.fn()
+vi.mock('axios');
+vi.mock('../../server/utils/logger', () => ({
+  logToFile: vi.fn()
 }));
 
 describe('Download Clients Integration Tests', () => {