Fix duplicate item display immediately after adding to shopping list

app/main.py

@@ -1181,8 +1181,9 @@ async def api_add_shopping_item(payload: ShoppingItemCreate):
         category=payload.category,
         note=payload.note or ""
     )
-    await shopping_ws_manager.broadcast({"action": "items_updated", "items": get_shopping_list()})
+    current_items = get_shopping_list()
-    return {"status": "ok", "item": item}
+    await shopping_ws_manager.broadcast({"action": "items_updated", "items": current_items})
+    return {"status": "ok", "item": item, "items": current_items}
 
 
 @app.put("/api/shopping-list/{item_id}")

app/templates/shopping_list.html

@@ -955,10 +955,25 @@
       localStorage.setItem('wtc_shop_cats_cache', JSON.stringify(allCategories));
     }
 
+    function deduplicateItems(items) {
+      if (!Array.isArray(items)) return [];
+      const seenIds = new Set();
+      const unique = [];
+      for (const item of items) {
+        if (!item) continue;
+        const key = item.id ? `id_${item.id}` : `name_${(item.item_name || '').toLowerCase().trim()}_${item.checked ? '1' : '0'}`;
+        if (!seenIds.has(key)) {
+          seenIds.add(key);
+          unique.push(item);
+        }
+      }
+      return unique;
+    }
+
     function saveLocalCache(items) {
-      allItems = items;
+      allItems = deduplicateItems(items);
       try {
-        localStorage.setItem('wtc_shop_items_cache', JSON.stringify(items));
+        localStorage.setItem('wtc_shop_items_cache', JSON.stringify(allItems));
       } catch (e) {
         console.warn('LocalStorage voll oder nicht verfügbar:', e);
       }
@@ -1227,8 +1242,8 @@
       const emptyState = document.getElementById('empty-state');
       if (!container) return;
 
-      // Filter anwenden
+      // Filter anwenden (dedupliziert gegen parallele WebSocket- & Fetch-Ereignisse)
-      let filtered = allItems;
+      let filtered = deduplicateItems(allItems);
       if (currentFilterCategory !== null) {
         filtered = filtered.filter(it => (it.category || 'Sonstiges') === currentFilterCategory);
       }
@@ -1459,12 +1474,19 @@
         });
         if (res.ok) {
           const data = await res.json();
-          if (data.item) {
+          if (data.items && Array.isArray(data.items)) {
+            allItems = data.items;
+          } else if (data.item) {
+            const existingIdx = allItems.findIndex(it => it.id === data.item.id);
+            if (existingIdx >= 0) {
+              allItems[existingIdx] = data.item;
+            } else {
               allItems.push(data.item);
+            }
+          }
           saveLocalCache(allItems);
           renderShoppingList();
           renderCategoryFilterChips();
-          }
         } else {
           throw new Error('Server-Fehler');
         }
@@ -1480,7 +1502,12 @@
           checked: false,
           source: ''
         };
+        const existingIdx = allItems.findIndex(it => (it.item_name || '').toLowerCase().trim() === name.toLowerCase().trim() && !it.checked);
+        if (existingIdx >= 0) {
+          allItems[existingIdx] = tempItem;
+        } else {
           allItems.push(tempItem);
+        }
         pushOfflineQueue({ method: 'POST', url: '/api/shopping-list', body: payload });
         saveLocalCache(allItems);
         renderShoppingList();