fix: 收藏夹弹窗优化 — 已收藏标识 + 移除确认 + 点击可靠性

- 收藏夹选项中已收藏项显示黄色'已收藏'徽章，一目了然
- 点击判断改用 classList.contains('active') 替代 JS 变量，防 currentFolderId 为空
- addToFolder 兜底处理'已在此收藏夹中'错误，不弹 alert
- 取消收藏确认文案优化为'确定移出该收藏夹吗？'

templates/MetaLab-2026/static/css/posts.css

@@ -927,6 +927,17 @@
     color: #9ca3af;
 }
 
+.fav-active-tag {
+    font-size: 11px;
+    color: #f59e0b;
+    background: #fef3c7;
+    padding: 1px 6px;
+    border-radius: 4px;
+    font-weight: 500;
+    flex-shrink: 0;
+    margin-right: 4px;
+}
+
 .fav-folder-opt-count {
     font-size: 12px;
     color: #9ca3af;

templates/MetaLab-2026/static/js/post-favorite.js

@@ -47,6 +47,7 @@
             var isActive = currentFolderId === f.id;
             html += '<div class="fav-folder-option' + (isActive ? ' active' : '') + '" data-id="' + f.id + '">'
                 + '<span class="fav-folder-opt-name">' + escapeHtml(f.name) + (f.is_default ? ' <small>(默认)</small>' : '') + '</span>'
+                + (isActive ? '<span class="fav-active-tag">已收藏</span>' : '')
                 + '<span class="fav-folder-opt-count">' + (f.item_count || 0) + ' 篇</span>'
                 + '</div>';
         });
@@ -110,6 +111,11 @@
                     updateBtn(true);
                     if (favCountEl) favCountEl.textContent = (parseInt(favCountEl.textContent) || 0) + 1;
                     hideModal();
+                } else if (d.message && d.message.indexOf('已在此收藏夹中') !== -1) {
+                    // 后端返回已收藏，直接关闭弹窗（兜底）
+                    currentFolderId = folderId;
+                    updateBtn(true);
+                    hideModal();
                 } else {
                     alert(d.message || '操作失败');
                 }
@@ -119,7 +125,7 @@
 
     function removeFromFolder(folderId) {
         if (loading) return;
-        showConfirm('确认', '确定取消收藏吗？').then(function(ok) {
+        showConfirm('确认取消收藏', '确定移出该收藏夹吗？').then(function(ok) {
             if (!ok) return;
             loading = true;
             api('DELETE', '/api/folders/' + folderId + '/posts/' + postId)
@@ -194,7 +200,7 @@
             if (!option) return;
             var folderId = parseInt(option.getAttribute('data-id'));
             if (isNaN(folderId)) return;
-            if (currentFolderId === folderId) {
+            if (option.classList.contains('active')) {
                 removeFromFolder(folderId);
             } else {
                 addToFolder(folderId);