Fix: prevent fileInput.js from adding event listeners more than once (#2365)

Fix fileInput.js adding event listeners more than once

- Fix a bug that caused fileInput.js to add event listeners more than once per HTML file as it's included in fileSelector fragment in fragments/common.html thus it's being loaded N times where N is the number of file selectors / custom file chooser / file input elements per HTML file, which resulted in each event actions being executed N times as well, which was prevalent in drag and drop operations such as dragging and dropping a file called y.png, it would be duplicated N times (as in /sign path).

src/main/resources/static/js/fileInput.js

@@ -1,6 +1,10 @@
-document.addEventListener("DOMContentLoaded", function () {
+let isScriptExecuted = false;
+if (!isScriptExecuted) {
+  isScriptExecuted = true;
+  document.addEventListener("DOMContentLoaded", function () {
     document.querySelectorAll(".custom-file-chooser").forEach(setupFileInput);
-});
+  });
+}
 
 function setupFileInput(chooser) {
   const elementId = chooser.getAttribute("data-bs-element-id");