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/new.vue

@@ -19,15 +19,17 @@
           </div>
         </div>
 
-        <TypeEditForm
-          :key="formKey"
-          v-model="draftType"
-          :saving="creating"
-          :resettable="false"
-          submit-label="Créer le type"
-          submit-loading-label="Création..."
-          @submit="handleSubmit"
-        />
+        <div :class="{ 'pointer-events-none opacity-60': !canEdit }">
+          <TypeEditForm
+            :key="formKey"
+            v-model="draftType"
+            :saving="!canEdit || creating"
+            :resettable="false"
+            submit-label="Créer le type"
+            submit-loading-label="Création..."
+            @submit="handleSubmit"
+          />
+        </div>
       </div>
     </div>
 
@@ -94,6 +96,7 @@ import IconLucideBox from '~icons/lucide/box'
 
 const { machineTypes, loadMachineTypes, createMachineType } = useMachineTypesApi()
 const { showError } = useToast()
+const { canEdit } = usePermissions()
 
 const formKey = ref(0)
 const creating = ref(false)