Function initUpload

public/js/upload.js:1770–1892

()

   Main initUpload: Sets up file input, drop area, and form submission.
----------------------------------------------------- */
function initUpload() {
  window.__FR_FLAGS = window.__FR_FLAGS || { wired: {} };
  window.__FR_FLAGS.wired = window.__FR_FLAGS.wired || {};

  const uploadForm = document.getElementById("uploadFileForm");
  const dropArea   = document.getElementById("uploadDropArea");

  // Always (re)build the inner markup and wire the Choose button
  setDropAreaDefault();
  wireChooseButton();

  const fileInput = document.getElementById("file");

  // For file picker, remove directory attributes so only files can be chosen.
  if (fileInput) {
    fileInput.removeAttribute("webkitdirectory");
    fileInput.removeAttribute("mozdirectory");
    fileInput.removeAttribute("directory");
    fileInput.setAttribute("multiple", "");
  }

  // Drag–and–drop events use Resumable when available, XHR as fallback.
  if (dropArea && !dropArea.__uploadBound) {
    dropArea.__uploadBound = true;
    dropArea.classList.add("upload-drop-area");

    dropArea.addEventListener("dragover", function (e) {
      e.preventDefault();
      dropArea.style.backgroundColor = document.body.classList.contains("dark-mode") ? "#333" : "#f8f8f8";
    });

    dropArea.addEventListener("dragleave", function (e) {
      e.preventDefault();
      dropArea.style.backgroundColor = "";
    });

    dropArea.addEventListener("drop", function (e) {
      e.preventDefault();
      dropArea.style.backgroundColor = "";
      const dt = e.dataTransfer || window.__pendingDropData || null;
      window.__pendingDropData = null;
      if (dt && dt.items && dt.items.length > 0) {
        getFilesFromDataTransferItems(dt.items).then(files => {
          if (files.length > 0) {
            queueResumableFiles(files);
          }
        });
      } else if (dt && dt.files && dt.files.length > 0) {
        queueResumableFiles(Array.from(dt.files));
      }
    });

    // Only trigger file picker when clicking the *bare* drop area, not controls inside it
    dropArea.addEventListener("click", function (e) {
      // If the click originated from the "Choose files" button or the file input itself,
      // let their handlers deal with it.
      if (e.target.closest('#customChooseBtn') || e.target.closest('#file')) {
        return;