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/admin-requests.routes.test.ts

@@ -0,0 +1,78 @@
+/**
+ * Component: Admin Requests API Route Tests
+ * Documentation: documentation/testing.md
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { createPrismaMock } from '../helpers/prisma';
+
+let authRequest: any;
+
+const prismaMock = createPrismaMock();
+const requireAuthMock = vi.hoisted(() => vi.fn());
+const requireAdminMock = vi.hoisted(() => vi.fn());
+const deleteRequestMock = vi.hoisted(() => vi.fn());
+
+vi.mock('@/lib/db', () => ({
+  prisma: prismaMock,
+}));
+
+vi.mock('@/lib/middleware/auth', () => ({
+  requireAuth: requireAuthMock,
+  requireAdmin: requireAdminMock,
+}));
+
+vi.mock('@/lib/services/request-delete.service', () => ({
+  deleteRequest: deleteRequestMock,
+}));
+
+describe('Admin requests routes', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    authRequest = { user: { id: 'admin-1', role: 'admin' } };
+    requireAuthMock.mockImplementation((_req: any, handler: any) => handler(authRequest));
+    requireAdminMock.mockImplementation((_req: any, handler: any) => handler());
+  });
+
+  it('returns recent requests', async () => {
+    prismaMock.request.findMany.mockResolvedValueOnce([
+      {
+        id: 'req-1',
+        status: 'pending',
+        createdAt: new Date(),
+        completedAt: null,
+        errorMessage: null,
+        audiobook: { title: 'Title', author: 'Author' },
+        user: { plexUsername: 'user' },
+        downloadHistory: [{ torrentUrl: 'http://torrent' }],
+      },
+    ]);
+
+    const { GET } = await import('@/app/api/admin/requests/recent/route');
+    const response = await GET({} as any);
+    const payload = await response.json();
+
+    expect(payload.requests).toHaveLength(1);
+    expect(payload.requests[0].torrentUrl).toBe('http://torrent');
+  });
+
+  it('soft deletes a request via delete service', async () => {
+    deleteRequestMock.mockResolvedValueOnce({
+      success: true,
+      message: 'Deleted',
+      filesDeleted: 1,
+      torrentsRemoved: 0,
+      torrentsKeptSeeding: 0,
+      torrentsKeptUnlimited: 0,
+    });
+
+    const { DELETE } = await import('@/app/api/admin/requests/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'req-1' }) });
+    const payload = await response.json();
+
+    expect(payload.success).toBe(true);
+    expect(deleteRequestMock).toHaveBeenCalledWith('req-1', 'admin-1');
+  });
+});
+
+