feat: automatically update copyright year

- Wrapped the copyright year in index.html with a span id="currentYear".
- Added JavaScript to script.js to dynamically set the year to the current year.

index.html

@@ -474,7 +474,7 @@
           >
         </p>
         <p class="mt-1">
-          Copyright &copy; 2025
+          Copyright &copy; <span id="currentYear">2025</span>
           <a
             href="https://xi-xu.me"
             target="_blank"

script.js

@@ -696,6 +696,12 @@ document.addEventListener("DOMContentLoaded", () => {
   updateSwapButtonState(); // Initialize swap button state
   lucide.createIcons(); // Initialize Lucide icons
 
+  // Update copyright year
+  const currentYearElement = document.getElementById("currentYear");
+  if (currentYearElement) {
+    currentYearElement.textContent = new Date().getFullYear();
+  }
+
   // Initial auto-translate if there's existing text
   if (elements.inputText.value.trim()) {
     scheduleAutoTranslate();