async function handleUpload(e) {
  e.preventDefault();
  const fileInput = document.getElementById('res-file');
  const file = fileInput.files[0];

  if (file.type !== "application/pdf" || file.size > 2097152) {
    ApexApp.showToast("File must be a PDF and under 2MB!", true);
    return;
  }

  const filePath = `res-${Date.now()}-${file.name.replace(/\s+/g, '_')}`;

  const { error: uploadError } = await supabase.storage
    .from('study-resources')
    .upload(filePath, file);

  if (uploadError) {
    ApexApp.showToast(uploadError.message, true);
    return;
  }

  const { data: { publicUrl } } = supabase.storage
    .from('study-resources')
    .getPublicUrl(filePath);

  // Insert resource metadata record
  const { error: dbError } = await supabase.from('resources').insert([{
    teacher_id: user.id,
    title: document.getElementById('res-title').value,
    category: document.getElementById('res-category').value,
    file_url: publicUrl,
    file_size_mb: Number((file.size / (1024 * 1024)).toFixed(2))
  }]);

  if (dbError) {
    ApexApp.showToast(dbError.message, true);
    return;
  }

  ApexApp.showToast("Study material uploaded!");
  closeUploadModal();
  renderResources();
}