feat(ui) : clickable entity links, site→machines links, DataTable fixedLayout

- Add NuxtLink on component/piece/product names in machine hierarchy
  (using composantId, pieceId, product.id)
- Make site machine count badges clickable → /machines?sites={id}
- Add opt-in fixedLayout prop and minWidth to DataTable columns

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/app/components/sites/SiteCard.vue

@@ -11,13 +11,14 @@
         <h3 class="card-title text-lg text-base-content">
           {{ site.name }}
         </h3>
-        <div
-          class="badge font-bold"
+        <NuxtLink
+          :to="`/machines?sites=${site.id}`"
+          class="badge font-bold hover:opacity-80 transition-opacity"
           :style="site.color ? { backgroundColor: site.color + '30', color: site.color, borderColor: site.color + '50' } : {}"
           :class="!site.color ? 'badge-primary' : ''"
         >
           {{ machineCount }} machines
-        </div>
+        </NuxtLink>
       </div>
 
       <div class="space-y-3 text-sm">
@@ -39,10 +40,10 @@
           </span>
         </div>
 
-        <div class="flex items-center gap-2 text-base-content/60">
+        <NuxtLink :to="`/machines?sites=${site.id}`" class="flex items-center gap-2 text-base-content/60 hover:text-primary transition-colors">
           <IconLucideFactory class="w-4 h-4 text-blue-500" aria-hidden="true" />
           <span>{{ machineCount }} machine(s)</span>
-        </div>
+        </NuxtLink>
       </div>
 
       <div class="card-actions justify-end mt-4">