Enhance NormalCaseFilter to support flexible age filtering with unit selection; update normals_list template with detailed help text for improved user guidance

atlas/templates/atlas/normals_list.html

@@ -1,10 +1,19 @@
 {% extends "atlas/base.html" %}
 {% load static %}
 {% load crispy_forms_tags %}
+{% load help_tags %}
 
 {% block content %}
   <div class="container">
     <h1>Normals</h1>
+    {% help "Help" %}
+      <p>This page lists all normal cases available in the atlas.</p>
+      <p>You can use the filter form to narrow down the list based on criteria such as age, modality, or examination type.</p>
+      <p>Click on a case title to view the case.</p>
+
+      <p>See a case that isn't normal? Please add feedback to the case so it can be reviewed.</p>
+
+    {% endhelp%}
 
     <div class="row mb-3">
       <div class="col-md-4">
@@ -54,3 +63,5 @@
     </nav>
   </div>
 {% endblock %}
+
+{% block css %}{% endblock %}