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/components/sites/SiteCreateModal.vue

@@ -12,17 +12,18 @@
             type="text"
             placeholder="Ex: Usine principale"
             class="input input-bordered"
+            :disabled="disabled"
             required
           />
         </div>
 
-        <SiteContactFormFields :form="siteRef" />
+        <SiteContactFormFields :form="siteRef" :disabled="disabled" />
 
         <div class="modal-action">
           <button type="button" class="btn" @click="emit('close')">
             Annuler
           </button>
-          <button type="submit" class="btn btn-primary">
+          <button type="submit" class="btn btn-primary" :disabled="disabled">
             Créer le site
           </button>
         </div>
@@ -53,6 +54,10 @@ const props = defineProps({
   site: {
     type: Object as PropType<SiteForm>,
     required: true
+  },
+  disabled: {
+    type: Boolean,
+    default: false
   }
 })