Gate sub-components section on eligible devices via can_have_subcomponents()

models.py

@@ -76,6 +76,9 @@ class Device(Base):
     def is_subcomponent(self):
         return self.parent_id is not None
 
+    def can_have_subcomponents(self):
+        return self.parent_id is None and self.battery_slots == 0
+
     def effective_installed_count(self):
         if self.has_children():
             return sum(c.installed_count() for c in self.children)

templates/device_detail.html

@@ -108,7 +108,7 @@
   </table>
 </div>
 
-{% if device.children or not device.is_subcomponent() %}
+{% if device.children or device.can_have_subcomponents() %}
 <div class="card">
   {% if device.children %}
   <h2>Sub-components</h2>