feat: 文章详情页右下角悬浮操作栏 + 作者自赋能拦截

- 赞/踩/赋能/收藏/评论/回顶部移至右下角悬浮操作栏，固定定位
- 回顶部按钮页面顶部隐藏，滚动后显示，平滑滚动
- 评论按钮点击定位到评论区（NAV 下方）
- 赋能按钮作者可见但禁止自赋能，点击弹出 toast 提示
- 未登录用户赋能/收藏点击跳转登录页
- postReactions 引用统一改为 postFloatBar

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

@@ -1248,3 +1248,85 @@
     font-size: 11px;
     margin-left: 8px;
 }
+
+/* ========== 右下角悬浮操作栏 ========== */
+.post-float-bar {
+    position: fixed;
+    right: 20px;
+    bottom: 120px;
+    display: flex;
+    flex-direction: column;
+    gap: 4px;
+    z-index: 100;
+    background: var(--color-surface, #fff);
+    border-radius: 12px;
+    box-shadow: 0 4px 24px rgba(0,0,0,.1);
+    padding: 6px;
+}
+
+.float-btn {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    width: 44px;
+    height: 44px;
+    border: none;
+    background: transparent;
+    border-radius: 8px;
+    cursor: pointer;
+    color: #6b7280;
+    transition: all .15s;
+    position: relative;
+}
+
+.float-btn:hover {
+    background: #f3f4f6;
+    color: #6366f1;
+}
+
+.float-btn.active {
+    color: #6366f1;
+    background: #eef2ff;
+}
+
+.float-btn svg {
+    width: 20px;
+    height: 20px;
+}
+
+.float-count {
+    font-size: 10px;
+    font-weight: 600;
+    line-height: 1;
+    margin-top: 2px;
+    color: inherit;
+}
+
+.float-top-btn {
+    border-top: 1px solid #f3f4f6;
+    border-radius: 0 0 8px 8px;
+    margin-top: 2px;
+    padding-top: 6px;
+}
+
+/* 赋能 Toast */
+.energize-toast {
+    position: fixed;
+    top: 80px;
+    left: 50%;
+    transform: translateX(-50%);
+    background: #1f2937;
+    color: #fff;
+    padding: 10px 24px;
+    border-radius: 8px;
+    font-size: 14px;
+    opacity: 0;
+    transition: opacity .3s;
+    z-index: 10000;
+    pointer-events: none;
+}
+
+.energize-toast.show {
+    opacity: 1;
+}