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/AudiobookshelfStep.test.tsx

@@ -0,0 +1,83 @@
+/**
+ * Component: Setup Audiobookshelf 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 { AudiobookshelfStep } from '@/app/setup/steps/AudiobookshelfStep';
+
+const AudiobookshelfHarness = ({
+  onNext,
+  onBack,
+  initialState,
+}: {
+  onNext: () => void;
+  onBack: () => void;
+  initialState?: Partial<React.ComponentProps<typeof AudiobookshelfStep>>;
+}) => {
+  const [state, setState] = useState({
+    absUrl: 'http://abs.local',
+    absApiToken: 'token',
+    absLibraryId: '',
+    absTriggerScanAfterImport: false,
+    ...initialState,
+  });
+
+  return (
+    <AudiobookshelfStep
+      {...state}
+      onUpdate={(field, value) => setState((prev) => ({ ...prev, [field]: value }))}
+      onNext={onNext}
+      onBack={onBack}
+    />
+  );
+};
+
+describe('AudiobookshelfStep', () => {
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it('requires library selection after successful test', async () => {
+    const fetchMock = vi.fn().mockResolvedValue({
+      ok: true,
+      json: async () => ({
+        success: true,
+        libraries: [{ id: 'lib-1', name: 'Main', itemCount: 10 }],
+      }),
+    });
+    vi.stubGlobal('fetch', fetchMock);
+    const onNext = vi.fn();
+
+    render(<AudiobookshelfHarness onNext={onNext} onBack={vi.fn()} />);
+
+    fireEvent.click(screen.getByRole('button', { name: 'Test Connection' }));
+
+    await waitFor(() => {
+      expect(fetchMock).toHaveBeenCalledWith('/api/setup/test-abs', expect.any(Object));
+    });
+
+    await screen.findByText('Connection successful!');
+
+    fireEvent.click(screen.getByRole('button', { name: 'Next' }));
+    expect(screen.getByText('Please select an audiobook library')).toBeInTheDocument();
+    expect(onNext).not.toHaveBeenCalled();
+
+    fireEvent.click(screen.getByRole('button', { name: 'Test Connection' }));
+    await screen.findByText('Connection successful!');
+
+    const librarySelect = await screen.findByRole('combobox');
+    fireEvent.change(librarySelect, { target: { value: 'lib-1' } });
+
+    await waitFor(() => {
+      expect(librarySelect).toHaveValue('lib-1');
+    });
+
+    fireEvent.click(screen.getByRole('button', { name: 'Next' }));
+    expect(onNext).toHaveBeenCalled();
+  });
+});