feat: secure and document book reviews system

Added rate limiting to APIs, cleaned up docs, implemented fallback logic for reviews without text, and added comprehensive n8n guide.

app/__tests__/components/ThemeToggle.test.tsx

@@ -0,0 +1,53 @@
+import React from "react";
+import { render, screen, fireEvent, waitFor } from "@testing-library/react";
+import { ThemeToggle } from "@/app/components/ThemeToggle";
+import { useTheme } from "next-themes";
+
+// Mock next-themes
+jest.mock("next-themes", () => ({
+  useTheme: jest.fn(),
+}));
+
+describe("ThemeToggle Component", () => {
+  const setThemeMock = jest.fn();
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    (useTheme as jest.Mock).mockReturnValue({
+      theme: "light",
+      setTheme: setThemeMock,
+    });
+  });
+
+  it("renders a placeholder initially (to avoid hydration mismatch)", () => {
+    const { container } = render(<ThemeToggle />);
+    // Initial render should be the loading div
+    expect(container.firstChild).toHaveClass("w-9 h-9");
+  });
+
+  it("toggles to dark mode when clicked", async () => {
+    render(<ThemeToggle />);
+    
+    // Wait for effect to set mounted=true
+    const button = await screen.findByRole("button", { name: /toggle theme/i });
+    
+    fireEvent.click(button);
+    
+    expect(setThemeMock).toHaveBeenCalledWith("dark");
+  });
+
+  it("toggles to light mode when clicked if currently dark", async () => {
+    (useTheme as jest.Mock).mockReturnValue({
+      theme: "dark",
+      setTheme: setThemeMock,
+    });
+
+    render(<ThemeToggle />);
+    
+    const button = await screen.findByRole("button", { name: /toggle theme/i });
+    
+    fireEvent.click(button);
+    
+    expect(setThemeMock).toHaveBeenCalledWith("light");
+  });
+});