Add series fields to audiobooks and update related logic

Introduces 'series' and 'seriesPart' fields to the Audiobook model and database schema. Updates API routes, file organization, and path template utilities to support series metadata. Enhances chapter merging logic, improves notification backend testing, and expands test coverage for admin and API routes.

tests/app/setup/steps/DownloadClientStep.test.tsx

@@ -0,0 +1,156 @@
+/**
+ * Component: Setup Download Client Step Tests
+ * Documentation: documentation/setup-wizard.md
+ */
+
+// @vitest-environment jsdom
+
+import React, { useState } from 'react';
+import { fireEvent, render, screen, waitFor } from '@testing-library/react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { DownloadClientStep } from '@/app/setup/steps/DownloadClientStep';
+
+const DownloadClientHarness = ({
+  onNext,
+  onBack,
+  initialState,
+}: {
+  onNext: () => void;
+  onBack: () => void;
+  initialState?: Partial<React.ComponentProps<typeof DownloadClientStep>>;
+}) => {
+  const [state, setState] = useState({
+    downloadClient: 'qbittorrent' as const,
+    downloadClientUrl: 'https://qbittorrent.local',
+    downloadClientUsername: 'admin',
+    downloadClientPassword: 'secret',
+    disableSSLVerify: false,
+    remotePathMappingEnabled: false,
+    remotePath: '',
+    localPath: '',
+    ...initialState,
+  });
+
+  return (
+    <DownloadClientStep
+      {...state}
+      onUpdate={(field, value) => setState((prev) => ({ ...prev, [field]: value }))}
+      onNext={onNext}
+      onBack={onBack}
+    />
+  );
+};
+
+describe('DownloadClientStep', () => {
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it('tests connection and enables navigation after success', async () => {
+    const fetchMock = vi.fn().mockResolvedValue({
+      ok: true,
+      json: async () => ({ success: true, version: '1.2.3' }),
+    });
+    vi.stubGlobal('fetch', fetchMock);
+    const onNext = vi.fn();
+
+    render(<DownloadClientHarness onNext={onNext} onBack={vi.fn()} />);
+
+    fireEvent.click(screen.getByRole('button', { name: 'Test Connection' }));
+
+    await waitFor(() => {
+      expect(fetchMock).toHaveBeenCalledWith('/api/setup/test-download-client', expect.any(Object));
+    });
+
+    expect(screen.getByText(/Connected successfully!/)).toBeInTheDocument();
+
+    fireEvent.click(screen.getByRole('button', { name: 'Next' }));
+    expect(onNext).toHaveBeenCalled();
+  });
+
+  it('shows remote path fields and toggles SSL verify', async () => {
+    render(<DownloadClientHarness onNext={vi.fn()} onBack={vi.fn()} />);
+
+    const sslToggle = screen.getByLabelText('Disable SSL Certificate Verification');
+    fireEvent.click(sslToggle);
+    expect(sslToggle).toBeChecked();
+
+    const remoteToggle = screen.getByLabelText('Enable Remote Path Mapping');
+    fireEvent.click(remoteToggle);
+
+    expect(screen.getByPlaceholderText('/remote/mnt/d/done')).toBeInTheDocument();
+    expect(screen.getByPlaceholderText('/downloads')).toBeInTheDocument();
+  });
+
+  it('switches to SABnzbd and shows API key field', async () => {
+    render(
+      <DownloadClientHarness
+        onNext={vi.fn()}
+        onBack={vi.fn()}
+        initialState={{ downloadClient: 'qbittorrent' }}
+      />
+    );
+
+    fireEvent.click(screen.getByRole('button', { name: /SABnzbd/ }));
+
+    expect(screen.getByText('API Key')).toBeInTheDocument();
+    expect(screen.queryByText('Username')).toBeNull();
+  });
+
+  it('blocks next when connection has not been tested', async () => {
+    const onNext = vi.fn();
+    render(<DownloadClientHarness onNext={onNext} onBack={vi.fn()} />);
+
+    fireEvent.click(screen.getByRole('button', { name: 'Next' }));
+
+    expect(screen.getByText('Please test the connection before proceeding')).toBeInTheDocument();
+    expect(onNext).not.toHaveBeenCalled();
+  });
+
+  it('shows an error when the connection test fails', async () => {
+    const fetchMock = vi.fn().mockResolvedValue({
+      ok: false,
+      json: async () => ({ error: 'Bad credentials' }),
+    });
+    vi.stubGlobal('fetch', fetchMock);
+
+    render(<DownloadClientHarness onNext={vi.fn()} onBack={vi.fn()} />);
+
+    fireEvent.click(screen.getByRole('button', { name: 'Test Connection' }));
+
+    await waitFor(() => {
+      expect(fetchMock).toHaveBeenCalledWith('/api/setup/test-download-client', expect.any(Object));
+    });
+
+    expect(screen.getByText('Bad credentials')).toBeInTheDocument();
+  });
+
+  it('disables test connection when SABnzbd fields are incomplete', async () => {
+    render(
+      <DownloadClientHarness
+        onNext={vi.fn()}
+        onBack={vi.fn()}
+        initialState={{
+          downloadClient: 'sabnzbd',
+          downloadClientUrl: '',
+          downloadClientPassword: '',
+        }}
+      />
+    );
+
+    const testButton = screen.getByRole('button', { name: 'Test Connection' });
+    expect(testButton).toBeDisabled();
+  });
+
+  it('hides SSL toggle when using http URLs', async () => {
+    render(
+      <DownloadClientHarness
+        onNext={vi.fn()}
+        onBack={vi.fn()}
+        initialState={{ downloadClientUrl: 'http://qbittorrent.local' }}
+      />
+    );
+
+    expect(screen.queryByLabelText('Disable SSL Certificate Verification')).toBeNull();
+  });
+});