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/[id].vue

@@ -163,6 +163,7 @@ import IconLucideAlertTriangle from '~icons/lucide/alert-triangle'
 
 const route = useRoute()
 const machineId = route.params.id
+const { canEdit } = usePermissions()
 
 if (!machineId) {
   console.error('ID de machine manquant')
@@ -212,7 +213,7 @@ onMounted(() => {
   d.loadMachineData()
   d.loadInitialData()
 
-  if (route.query.edit === 'true') {
+  if (route.query.edit === 'true' && canEdit.value) {
     d.isEditMode.value = true
   }
 })