Add backend unit test framework and modularize settings UI

Introduced a Vitest-based backend unit testing framework with supporting scripts, helpers, and GitHub Actions integration. Refactored the admin settings page to a modular architecture, splitting monolithic logic into feature-specific tabs and hooks for improved maintainability and testability. Updated documentation to reflect the new testing setup and settings architecture, and added new dependencies for testing utilities.

tests/api/audiobooks-request-torrent.routes.test.ts

@@ -0,0 +1,94 @@
+/**
+ * Component: Request With Torrent API Route Tests
+ * Documentation: documentation/testing.md
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { createPrismaMock } from '../helpers/prisma';
+
+let authRequest: any;
+
+const requireAuthMock = vi.hoisted(() => vi.fn());
+const prismaMock = createPrismaMock();
+const jobQueueMock = vi.hoisted(() => ({
+  addDownloadJob: vi.fn(),
+}));
+const findPlexMatchMock = vi.hoisted(() => vi.fn());
+
+vi.mock('@/lib/middleware/auth', () => ({
+  requireAuth: requireAuthMock,
+}));
+
+vi.mock('@/lib/db', () => ({
+  prisma: prismaMock,
+}));
+
+vi.mock('@/lib/services/job-queue.service', () => ({
+  getJobQueueService: () => jobQueueMock,
+}));
+
+vi.mock('@/lib/utils/audiobook-matcher', () => ({
+  findPlexMatch: findPlexMatchMock,
+}));
+
+describe('Request with torrent route', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    authRequest = {
+      user: { id: 'user-1', role: 'user' },
+      json: vi.fn(),
+    };
+    requireAuthMock.mockImplementation((_req: any, handler: any) => handler(authRequest));
+  });
+
+  it('returns 409 when audiobook is already being processed', async () => {
+    authRequest.json.mockResolvedValue({
+      audiobook: { asin: 'ASIN', title: 'Title', author: 'Author' },
+      torrent: { guid: 'guid', title: 'Torrent', size: 100, indexer: 'Indexer', downloadUrl: 'url', publishDate: '2024-01-01' },
+    });
+    prismaMock.request.findFirst.mockResolvedValueOnce({
+      id: 'req-1',
+      status: 'downloaded',
+      userId: 'user-2',
+      user: { plexUsername: 'other' },
+    });
+
+    const { POST } = await import('@/app/api/audiobooks/request-with-torrent/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(409);
+    expect(payload.error).toBe('BeingProcessed');
+  });
+
+  it('creates request and queues download job', async () => {
+    authRequest.json.mockResolvedValue({
+      audiobook: { asin: 'ASIN', title: 'Title', author: 'Author' },
+      torrent: { guid: 'guid', title: 'Torrent', size: 100, indexer: 'Indexer', downloadUrl: 'url', publishDate: '2024-01-01' },
+    });
+    prismaMock.request.findFirst.mockResolvedValueOnce(null);
+    findPlexMatchMock.mockResolvedValueOnce(null);
+    prismaMock.audiobook.findFirst.mockResolvedValueOnce(null);
+    prismaMock.audiobook.create.mockResolvedValueOnce({ id: 'ab-1', title: 'Title', author: 'Author', audibleAsin: 'ASIN' });
+    prismaMock.request.findFirst.mockResolvedValueOnce(null);
+    prismaMock.request.create.mockResolvedValueOnce({
+      id: 'req-2',
+      audiobook: { id: 'ab-1', title: 'Title', author: 'Author' },
+      user: { id: 'user-1', plexUsername: 'user' },
+    });
+
+    const { POST } = await import('@/app/api/audiobooks/request-with-torrent/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(201);
+    expect(payload.success).toBe(true);
+    expect(jobQueueMock.addDownloadJob).toHaveBeenCalledWith('req-2', {
+      id: 'ab-1',
+      title: 'Title',
+      author: 'Author',
+    }, expect.objectContaining({ guid: 'guid' }));
+  });
+});
+
+