Adding ability to autovivify an appropriate attachment point when manually entering a fit

app/templates/admin/_fit_other_points_select.html

@@ -1,6 +1,13 @@
+{% if points %}
 <select name="other_attachment_point_id" required>
   <option value="">— select —</option>
   {% for p in points %}
     <option value="{{ p.id }}">{{ p.attachment_point_name.name }}</option>
   {% endfor %}
 </select>
+{% else %}
+<input type="hidden" name="other_attachment_point_id" value="">
+<p class="muted" style="font-size:0.85rem;margin:0">
+  This part has no attachment points yet — one matching yours will be created automatically.
+</p>
+{% endif %}