refactor(ui) : improve styling, layout and responsive across all components

Rework CSS theme (app.css), navbar layout, dashboard page, machine detail,
catalog pages, and various form/display components for better consistency
and mobile responsiveness.

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

app/pages/sites.vue

@@ -24,11 +24,11 @@
 
       <div v-else-if="sites.length === 0" class="text-center py-12">
         <div class="max-w-md mx-auto">
-          <IconLucideMapPin class="w-16 h-16 mx-auto text-gray-400 mb-4" aria-hidden="true" />
-          <h3 class="text-lg font-medium text-gray-900 mb-2">
+          <IconLucideMapPin class="w-16 h-16 mx-auto text-base-content/30 mb-4" aria-hidden="true" />
+          <h3 class="text-lg font-medium text-base-content mb-2">
             Aucun site trouvé
           </h3>
-          <p class="text-gray-500 mb-4">
+          <p class="text-base-content/50 mb-4">
             Commencez par ajouter votre premier site.
           </p>
           <button v-if="canEdit" class="btn btn-primary" @click="openCreateSiteModal">