fix: 修复收藏夹列表加载失败 + 收藏按钮改为弹窗选择收藏夹

- settings/favorites 收藏夹列表加载失败：escapeHTML 在 energy Tab 闭包内，收藏夹 Tab 无法访问导致 ReferenceError，修复为本地 esc() 函数
- settings 创建/删除收藏夹请求缺少 CSRF Token（403），统一使用 fetch + X-CSRF-Token 头
- API 错误时显示实际错误信息而非吞掉显示"暂无收藏夹"
- 文章详情页收藏按钮：点击弹出选择收藏夹弹窗，列出所有收藏夹，已收藏的文章高亮显示
- 弹窗支持原地新建收藏夹并立即收藏（一键创建+收藏）
- 新增收藏夹弹窗 CSS 样式（.fav-overlay/.fav-modal/.fav-folder-option 等）

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

@@ -790,6 +790,184 @@
     font-weight: 500;
 }
 
+/* ========== 选择收藏夹弹窗 ========== */
+.fav-overlay {
+    position: fixed;
+    top: 0; left: 0; right: 0; bottom: 0;
+    background: rgba(0, 0, 0, 0.45);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    z-index: 9999;
+}
+
+.fav-modal {
+    background: #fff;
+    border-radius: 12px;
+    width: 400px;
+    max-width: 92vw;
+    max-height: 80vh;
+    display: flex;
+    flex-direction: column;
+    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.15);
+    overflow: hidden;
+}
+
+.fav-modal-header {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 20px 24px 16px;
+    border-bottom: 1px solid #f0f0f0;
+    flex-shrink: 0;
+}
+
+.fav-modal-header h3 {
+    margin: 0;
+    font-size: 18px;
+    font-weight: 600;
+    color: #111827;
+}
+
+.fav-close {
+    background: none;
+    border: none;
+    font-size: 24px;
+    color: #9ca3af;
+    cursor: pointer;
+    padding: 0;
+    line-height: 1;
+}
+
+.fav-close:hover {
+    color: #374151;
+}
+
+.fav-modal-body {
+    padding: 16px 24px;
+    overflow-y: auto;
+    flex: 1;
+}
+
+.fav-loading {
+    text-align: center;
+    padding: 24px 0;
+    font-size: 14px;
+    color: #9ca3af;
+}
+
+.fav-loading.fav-error {
+    color: #ef4444;
+}
+
+.fav-empty {
+    text-align: center;
+    padding: 24px 0;
+    font-size: 14px;
+    color: #9ca3af;
+}
+
+.fav-folder-list {
+    display: flex;
+    flex-direction: column;
+    gap: 4px;
+    margin-bottom: 16px;
+}
+
+.fav-folder-option {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 12px 14px;
+    border-radius: 8px;
+    border: 1px solid #e5e7eb;
+    cursor: pointer;
+    transition: all 0.15s ease;
+}
+
+.fav-folder-option:hover {
+    border-color: #f59e0b;
+    background: #fffbeb;
+}
+
+.fav-folder-option.active {
+    border-color: #f59e0b;
+    background: #fef3c7;
+    font-weight: 500;
+}
+
+.fav-folder-option.active::after {
+    content: "✓";
+    color: #f59e0b;
+    font-weight: 700;
+    font-size: 16px;
+}
+
+.fav-folder-opt-name {
+    font-size: 14px;
+    color: #1f2937;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+    margin-right: 8px;
+}
+
+.fav-folder-opt-name small {
+    font-weight: 400;
+    color: #9ca3af;
+}
+
+.fav-folder-opt-count {
+    font-size: 12px;
+    color: #9ca3af;
+    flex-shrink: 0;
+}
+
+.fav-new-folder {
+    display: flex;
+    gap: 8px;
+    align-items: center;
+}
+
+.fav-new-input {
+    flex: 1;
+    padding: 10px 14px;
+    border: 1px solid #d1d5db;
+    border-radius: 8px;
+    font-size: 14px;
+    font-family: inherit;
+    outline: none;
+    transition: border-color 0.15s;
+}
+
+.fav-new-input:focus {
+    border-color: #f59e0b;
+    box-shadow: 0 0 0 2px rgba(245, 158, 11, 0.15);
+}
+
+.fav-new-btn {
+    padding: 10px 16px;
+    border: none;
+    border-radius: 8px;
+    background: #f59e0b;
+    color: #fff;
+    font-size: 13px;
+    font-weight: 500;
+    font-family: inherit;
+    cursor: pointer;
+    transition: background 0.15s;
+    white-space: nowrap;
+}
+
+.fav-new-btn:hover {
+    background: #d97706;
+}
+
+.fav-new-btn:disabled {
+    opacity: 0.5;
+    cursor: not-allowed;
+}
+
 /* ========== 评论区 ========== */
 .comments-section {
     max-width: 800px;