feat(permissions) : add role-based UI guards and readonly mode for viewers

- Add usePermissions composable (isAdmin, canEdit, canView)
- Password-protected profile login with modal on profiles page
- Disable all form fields for ROLE_VIEWER across edit/create pages
- Show navigation buttons (Modifier/Consulter) for all roles, hide delete for viewers
- Add readonly prop to ModelTypeForm for category pages
- Disable modal fields (sites, constructeurs) for viewers
- Guard /admin routes in middleware

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

app/pages/machine-skeleton/index.vue

@@ -68,6 +68,7 @@
             </div>
             <div class="card-actions justify-end mt-4">
               <button
+                v-if="canEdit"
                 class="btn btn-sm btn-error"
                 @click.stop="confirmDeleteType(type)"
               >
@@ -108,6 +109,7 @@ import IconLucidePackage from "~icons/lucide/package";
 import IconLucideLayoutGrid from "~icons/lucide/layout-grid";
 import IconLucideBox from "~icons/lucide/box";
 
+const { canEdit } = usePermissions();
 const { machineTypes, loadMachineTypes, deleteMachineType } =
   useMachineTypesApi();