Add sponsor buttons for GitHub Sponsors and PayPal below the action bar with an intro message and tests

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: nolar

src/App.tsx

@@ -120,6 +120,27 @@ function App() {
               className="hidden"
             />
           </div>
+          <div className="mt-3 text-center print:hidden">
+            <p className="text-sm text-gray-500 mb-2">If you like the app, please support the author with bread &amp; beer:</p>
+            <div className="flex gap-2 justify-center">
+              <a
+                href="https://github.com/sponsors/nolar/"
+                target="_blank"
+                rel="noopener noreferrer"
+                className="rounded bg-gray-100 px-3 py-1.5 text-sm font-medium text-gray-700 hover:bg-gray-200"
+              >
+                Sponsor via GitHub
+              </a>
+              <a
+                href="https://paypal.me/nolarinfo"
+                target="_blank"
+                rel="noopener noreferrer"
+                className="rounded bg-gray-100 px-3 py-1.5 text-sm font-medium text-gray-700 hover:bg-gray-200"
+              >
+                Sponsor via PayPal
+              </a>
+            </div>
+          </div>
         </main>
         <aside className="w-64 shrink-0 print:hidden">
           <DateForm

src/__tests__/App.test.tsx

@@ -58,6 +58,23 @@ describe("App", () => {
     expect(downloadBtn.parentElement!.className).toContain("print:hidden");
   });
 
+  it("renders sponsor links with correct hrefs", () => {
+    render(<MemoryRouter><App /></MemoryRouter>);
+
+    const github = screen.getByRole("link", { name: "Sponsor via GitHub" });
+    expect(github).toHaveAttribute("href", "https://github.com/sponsors/nolar/");
+    expect(github).toHaveAttribute("target", "_blank");
+
+    const paypal = screen.getByRole("link", { name: "Sponsor via PayPal" });
+    expect(paypal).toHaveAttribute("href", "https://paypal.me/nolarinfo");
+    expect(paypal).toHaveAttribute("target", "_blank");
+  });
+
+  it("renders sponsor intro text", () => {
+    render(<MemoryRouter><App /></MemoryRouter>);
+    expect(screen.getByText(/support the author with bread & beer/)).toBeInTheDocument();
+  });
+
   it("applies print layout classes to root containers", () => {
     const { container } = render(<MemoryRouter><App /></MemoryRouter>);
     const root = container.firstElementChild!;