Persist language selection using localStorage

Language dropdowns now restore the user's last selected source and target languages from localStorage, or fall back to defaults if none are saved. Selections are saved on change, improving user experience by remembering preferences across sessions.

script.js

@@ -162,7 +162,7 @@ document.addEventListener("DOMContentLoaded", () => {
 
   /**
    * Populates language dropdown menus with sorted language options
-   * Sets default values for source (AUTO) and target (EN) languages
+   * Restores saved language selections or uses defaults
    */
   function populateLanguages() {
     elements.sourceLangSelect.innerHTML =
@@ -182,9 +182,12 @@ document.addEventListener("DOMContentLoaded", () => {
       elements.targetLangSelect.add(new Option(name, code));
     });
 
-    // Set default language selections
-    elements.sourceLangSelect.value = "AUTO";
-    elements.targetLangSelect.value = "EN";
+    // Restore saved language selections or use defaults
+    const savedSourceLang = localStorage.getItem("deeplxSourceLang") || "AUTO";
+    const savedTargetLang = localStorage.getItem("deeplxTargetLang") || "EN";
+
+    elements.sourceLangSelect.value = savedSourceLang;
+    elements.targetLangSelect.value = savedTargetLang;
   }
 
   // Load and save settings
@@ -719,8 +722,14 @@ document.addEventListener("DOMContentLoaded", () => {
   elements.sourceLangSelect.addEventListener("change", () => {
     updateSwapButtonState();
     scheduleAutoTranslate();
+    // Save source language selection
+    localStorage.setItem("deeplxSourceLang", elements.sourceLangSelect.value);
+  });
+  elements.targetLangSelect.addEventListener("change", () => {
+    scheduleAutoTranslate();
+    // Save target language selection
+    localStorage.setItem("deeplxTargetLang", elements.targetLangSelect.value);
   });
-  elements.targetLangSelect.addEventListener("change", scheduleAutoTranslate);
 
   // Panel management - close when clicking outside
   elements.historyPanel.addEventListener("click", (e) => {