bg-card will be added to the class and password/username validation

bg-card should not be an id, ids should be unique in their use.

src/main/resources/templates/convert/pdf-to-img.html

@@ -12,7 +12,7 @@
         <br><br>
         <div class="container">
           <div class="row justify-content-center">
-            <div class="col-md-6" id="bg-card">
+            <div class="col-md-6 bg-card">
               <div class="tool-header">
                 <span class="material-symbols-rounded tool-header-icon image">image</span>
                 <span class="tool-header-text" th:text="#{pdfToImage.header}"></span>