Add loading indicator for main items in admin view to enhance user experience

Web/templates/main.html

@@ -730,8 +730,43 @@
     let mainItemsLoadingMore = false;
     let mainItemsObserver = null;
     let mainItemsSentinel = null;
+    let mainItemsLoadingIndicator = null;
     let mainItemsScrollPrefetchBound = false;
 
+    function ensureMainItemsLoadingIndicator() {
+        const itemsContainer = document.querySelector('#items-container');
+        if (!itemsContainer) return null;
+
+        if (!mainItemsLoadingIndicator) {
+            mainItemsLoadingIndicator = document.createElement('div');
+            mainItemsLoadingIndicator.id = 'main-items-loading-indicator';
+            mainItemsLoadingIndicator.className = 'items-loading-indicator';
+            mainItemsLoadingIndicator.innerHTML = `
+                <div class="loading-track"><div class="loading-fill"></div></div>
+                <div class="loading-label">Weitere Objekte werden vorbereitet...</div>
+            `;
+        }
+
+        itemsContainer.appendChild(mainItemsLoadingIndicator);
+        return itemsContainer;
+    }
+
+    function updateMainItemsLoadingIndicator() {
+        const itemsContainer = ensureMainItemsLoadingIndicator();
+        if (!itemsContainer || !mainItemsLoadingIndicator) return;
+
+        const shouldShow = mainItemsHasMore || mainItemsLoadingMore;
+        mainItemsLoadingIndicator.style.display = shouldShow ? 'flex' : 'none';
+        mainItemsLoadingIndicator.classList.toggle('is-loading', mainItemsLoadingMore);
+
+        const label = mainItemsLoadingIndicator.querySelector('.loading-label');
+        if (label) {
+            label.textContent = mainItemsLoadingMore
+                ? 'Weitere Objekte werden geladen...'
+                : 'Weitere Objekte werden vorbereitet...';
+        }
+    }
+
     function maybePrefetchMainItems() {
         const itemsContainer = document.querySelector('#items-container');
         if (!itemsContainer || !mainItemsHasMore || mainItemsLoadingMore) {
@@ -745,8 +780,10 @@
         }
 
         mainItemsLoadingMore = true;
+        updateMainItemsLoadingIndicator();
         loadItems(mainItemsNextOffset, true).finally(() => {
             mainItemsLoadingMore = false;
+            updateMainItemsLoadingIndicator();
         });
     }
 
@@ -1054,11 +1091,15 @@
 
                 mainItemsNextOffset = (data.offset || offset) + (data.count || pageItems.length);
                 mainItemsHasMore = Boolean(data.has_more);
+                updateMainItemsLoadingIndicator();
                 setupMainItemsLazyLoading();
                 maybePrefetchMainItems();
             })
             .catch(error => {
                 console.error('Error fetching items:', error);
+                mainItemsLoadingMore = false;
+                mainItemsHasMore = false;
+                updateMainItemsLoadingIndicator();
                 if (append) {
                     return;
                 }
@@ -1072,6 +1113,8 @@
         const itemsContainer = document.querySelector('#items-container');
         if (!itemsContainer) return null;
 
+        ensureMainItemsLoadingIndicator();
+
         if (!mainItemsSentinel) {
             mainItemsSentinel = document.createElement('div');
             mainItemsSentinel.id = 'main-items-sentinel';
@@ -1117,8 +1160,10 @@
             }
 
             mainItemsLoadingMore = true;
+            updateMainItemsLoadingIndicator();
             loadItems(mainItemsNextOffset, true).finally(() => {
                 mainItemsLoadingMore = false;
+                updateMainItemsLoadingIndicator();
             });
         }, {
             root: itemsContainer,
@@ -1127,6 +1172,7 @@
         });
 
         mainItemsObserver.observe(mainItemsSentinel);
+        updateMainItemsLoadingIndicator();
     }
 
     function searchByCode() {
@@ -2846,6 +2892,57 @@
         scroll-behavior: smooth;
     }
 
+    .items-loading-indicator {
+        display: none;
+        flex: 0 0 220px;
+        min-width: 220px;
+        max-width: 220px;
+        height: 180px;
+        align-self: center;
+        margin-right: 8px;
+        border: 1px solid #dbe3ee;
+        border-radius: 10px;
+        background: #f8fafc;
+        color: #334155;
+        justify-content: center;
+        align-items: center;
+        flex-direction: column;
+        gap: 10px;
+        scroll-snap-align: center;
+    }
+
+    .items-loading-indicator .loading-label {
+        font-size: 0.84rem;
+        text-align: center;
+        line-height: 1.3;
+        max-width: 170px;
+    }
+
+    .items-loading-indicator .loading-track {
+        width: 160px;
+        height: 8px;
+        border-radius: 999px;
+        background: #e2e8f0;
+        overflow: hidden;
+    }
+
+    .items-loading-indicator .loading-fill {
+        width: 45%;
+        height: 100%;
+        border-radius: inherit;
+        background: linear-gradient(90deg, #60a5fa, #2563eb);
+        transform: translateX(-100%);
+    }
+
+    .items-loading-indicator.is-loading .loading-fill {
+        animation: items-loader-slide 1.05s ease-in-out infinite;
+    }
+
+    @keyframes items-loader-slide {
+        0% { transform: translateX(-100%); }
+        100% { transform: translateX(260%); }
+    }
+
     .item-card {
         background-color: #fff;
         border: 1px solid #ddd;