fix(ui) : move add buttons below last element in structure editors

Place "Ajouter" buttons after the items list instead of in the section
header, so they always appear below the last added element.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/components/machine/MachineComponentsCard.vue

@@ -3,31 +3,21 @@
     <div class="card-body">
       <div class="flex justify-between items-center mb-4">
         <h2 class="card-title">Composants</h2>
-        <div class="flex items-center gap-2">
-          <button
-            v-if="isEditMode"
-            type="button"
-            class="btn btn-sm md:btn-md btn-primary"
-            @click="$emit('add-component')"
-          >
-            Ajouter un composant
-          </button>
-          <button
-            type="button"
-            class="btn btn-ghost btn-sm gap-2"
-            @click="$emit('toggle-collapse')"
-            :title="collapsed ? 'Déplier tous les composants' : 'Replier tous les composants'"
-          >
-            <IconLucideChevronRight
-              class="w-5 h-5 transition-transform"
-              :class="collapsed ? 'rotate-0' : 'rotate-90'"
-              aria-hidden="true"
-            />
-            <span class="text-sm">
-              {{ collapsed ? 'Tout déplier' : 'Tout replier' }}
-            </span>
-          </button>
-        </div>
+        <button
+          type="button"
+          class="btn btn-ghost btn-sm gap-2"
+          @click="$emit('toggle-collapse')"
+          :title="collapsed ? 'Déplier tous les composants' : 'Replier tous les composants'"
+        >
+          <IconLucideChevronRight
+            class="w-5 h-5 transition-transform"
+            :class="collapsed ? 'rotate-0' : 'rotate-90'"
+            aria-hidden="true"
+          />
+          <span class="text-sm">
+            {{ collapsed ? 'Tout déplier' : 'Tout replier' }}
+          </span>
+        </button>
       </div>
 
       <div v-if="components.length === 0" class="text-sm text-gray-500 py-4">
@@ -54,6 +44,15 @@
           />
         </div>
       </div>
+
+      <button
+        v-if="isEditMode"
+        type="button"
+        class="btn btn-sm md:btn-md btn-primary"
+        @click="$emit('add-component')"
+      >
+        Ajouter un composant
+      </button>
     </div>
   </div>
 </template>