feat(ui) : add site colors, dark mode toggle and card styling improvements

- Site color field with color picker in create/edit modals
- Dark mode theme (mytheme-dark) with toggle in navbar
- Stronger site color visibility on cards (gradient, top border, badges)
- Bigger action buttons (btn-sm) on machine cards
- White card backgrounds with proper dark mode support

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

app/pages/component-catalog.vue

@@ -95,7 +95,7 @@
           </template>
 
           <template #cell-actions="{ row }">
-            <div class="flex items-center gap-2">
+            <div class="flex items-center justify-end gap-2">
               <NuxtLink
                 :to="`/component/${row.component.id}/edit`"
                 class="btn btn-ghost btn-xs"
@@ -105,7 +105,7 @@
               <button
                 v-if="canEdit"
                 type="button"
-                class="btn btn-error btn-xs"
+                class="btn btn-ghost btn-xs text-error"
                 :disabled="loadingComposants"
                 @click="handleDeleteComponent(row.component)"
               >