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/components/CustomFieldsDisplay.vue

@@ -1,6 +1,6 @@
 <template>
   <div v-if="customFields && customFields.length > 0" class="space-y-4">
-    <h4 class="font-semibold text-gray-700 mb-3">
+    <h4 class="font-semibold text-base-content/80 mb-3">
       Champs personnalisés
     </h4>
     <div class="grid grid-cols-1 md:grid-cols-2 gap-4">