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/comments.vue

@@ -4,7 +4,7 @@
       <h1 class="text-3xl font-semibold text-base-content">
         Commentaires
       </h1>
-      <p class="text-sm text-gray-500">
+      <p class="text-sm text-base-content/50">
         Liste de tous les commentaires et tickets ouverts sur les fiches.
       </p>
     </header>