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/component-category/[id]/edit.vue

@@ -26,6 +26,7 @@
         :initial-data="initialData"
         :lock-category="true"
         :saving="saving"
+        :readonly="!canEdit"
         :disable-submit="isSubmitBlocked"
         :disable-submit-message="submitBlockMessage"
         :restricted-mode="isRestrictedMode"
@@ -47,6 +48,7 @@ import { useCategoryEditGuard } from '~/composables/useCategoryEditGuard'
 import { useComponentTypes } from '~/composables/useComponentTypes'
 import { useToast } from '~/composables/useToast'
 
+const { canEdit } = usePermissions()
 const route = useRoute()
 const router = useRouter()
 const { showError, showSuccess } = useToast()
@@ -128,6 +130,7 @@ const handleCancel = () => {
 }
 
 const handleSubmit = async (payload: Parameters<typeof updateModelType>[1]) => {
+  if (!canEdit.value) return
   if (guardSubmitOrNotify()) {
     return
   }