Make invalid search input explicit in UI and API

templates/players/partials/results.html

@@ -7,6 +7,20 @@
   </div>
 </div>
 
+{% if search_has_errors %}
+  <div class="mt-3 rounded-md border border-rose-200 bg-rose-50 p-3 text-sm text-rose-800">
+    <p class="font-medium">Search filters are invalid.</p>
+    {% for field in search_form %}
+      {% for error in field.errors %}
+        <p>{{ field.label }}: {{ error }}</p>
+      {% endfor %}
+    {% endfor %}
+    {% for error in search_form.non_field_errors %}
+      <p>{{ error }}</p>
+    {% endfor %}
+  </div>
+{% endif %}
+
 {% if request.user.is_authenticated %}
   {% include "scouting/partials/save_search_form.html" %}
 {% endif %}