feat(ui): use modal dialogs for entity creation and editing

Introduce reusable Modal component for forms
Update router to preserve scroll position when toggling modals
Refactor admin and entity views to render editors as overlays

frontend/src/views/ItemDetail.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { computed, onMounted, ref } from 'vue';
+import { computed, onMounted, ref, watch } from 'vue';
 import { useI18n } from 'vue-i18n';
 import { useRoute } from 'vue-router';
 import DetailSection from '../components/DetailSection.vue';
@@ -8,10 +8,12 @@ import EntityChips from '../components/EntityChips.vue';
 import PageHeader from '../components/PageHeader.vue';
 import Skeleton from '../components/Skeleton.vue';
 import { api, type ItemDetail } from '../services/api';
+import ItemEdit from './ItemEdit.vue';
 
 const route = useRoute();
 const { t } = useI18n();
 const item = ref<ItemDetail | null>(null);
+const showEditor = computed(() => route.name === 'item-edit');
 
 const customization = computed(() => {
   if (!item.value) {
@@ -25,9 +27,30 @@ const customization = computed(() => {
   ].filter(Boolean);
 });
 
-onMounted(async () => {
+async function loadItemDetail() {
   item.value = await api.itemDetail(String(route.params.id));
+}
+
+onMounted(async () => {
+  await loadItemDetail();
 });
+
+watch(
+  () => route.name,
+  (name, oldName) => {
+    if (oldName === 'item-edit' && name === 'item-detail') {
+      void loadItemDetail();
+    }
+  }
+);
+
+watch(
+  () => route.params.id,
+  () => {
+    item.value = null;
+    void loadItemDetail();
+  }
+);
 </script>
 
 <template>
@@ -157,4 +180,6 @@ onMounted(async () => {
       <EditHistoryPanel :entity="item" :history="item.editHistory" />
     </div>
   </section>
+
+  <ItemEdit v-if="showEditor" />
 </template>