feat: Use unified button layout

src/fellchensammlung/templates/fellchensammlung/forms/form-report.html

@@ -7,6 +7,6 @@
     <form method = "post" enctype="multipart/form-data">
         {% csrf_token %}
         {{ form.as_p }}
-        <button class="button-report" type="submit">{% translate "Melden" %}</button>
+        <button class="btn2" type="submit">{% translate "Melden" %}</button>
     </form>
 {% endblock %}