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/components/ui/VersionBadge.test.tsx

@@ -0,0 +1,61 @@
+/**
+ * Component: Version Badge Tests
+ * Documentation: documentation/frontend/components.md
+ */
+
+// @vitest-environment jsdom
+
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { render, screen, waitFor } from '@testing-library/react';
+import { VersionBadge } from '@/components/ui/VersionBadge';
+
+const originalCommit = process.env.NEXT_PUBLIC_GIT_COMMIT;
+
+describe('VersionBadge', () => {
+  afterEach(() => {
+    vi.unstubAllGlobals();
+    if (originalCommit === undefined) {
+      delete process.env.NEXT_PUBLIC_GIT_COMMIT;
+    } else {
+      process.env.NEXT_PUBLIC_GIT_COMMIT = originalCommit;
+    }
+  });
+
+  it('renders short version from build-time commit', async () => {
+    process.env.NEXT_PUBLIC_GIT_COMMIT = 'abcdef1234';
+    const fetchMock = vi.fn();
+    vi.stubGlobal('fetch', fetchMock);
+
+    render(<VersionBadge />);
+
+    expect(await screen.findByText('v.abcdef1')).toBeInTheDocument();
+    expect(fetchMock).not.toHaveBeenCalled();
+  });
+
+  it('falls back to API when build-time commit is unavailable', async () => {
+    process.env.NEXT_PUBLIC_GIT_COMMIT = 'unknown';
+    const fetchMock = vi.fn().mockResolvedValue({
+      json: async () => ({ version: 'v.1.2.3' }),
+    });
+    vi.stubGlobal('fetch', fetchMock);
+
+    render(<VersionBadge />);
+
+    expect(await screen.findByText('v.1.2.3')).toBeInTheDocument();
+    expect(fetchMock).toHaveBeenCalledWith('/api/version');
+  });
+
+  it('shows dev version when API fetch fails', async () => {
+    process.env.NEXT_PUBLIC_GIT_COMMIT = 'unknown';
+    const fetchMock = vi.fn().mockRejectedValue(new Error('down'));
+    const errorMock = vi.spyOn(console, 'error').mockImplementation(() => undefined);
+    vi.stubGlobal('fetch', fetchMock);
+
+    render(<VersionBadge />);
+
+    await waitFor(() => {
+      expect(screen.getByText('v.dev')).toBeInTheDocument();
+    });
+    expect(errorMock).toHaveBeenCalledWith('Failed to fetch version:', expect.any(Error));
+  });
+});