feat(admin): 合并内容审核到内容管理，并固定后台侧栏

待审与内容库同一页处理；筛选切换去掉加载占位，避免页面闪动。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/app/globals.css

@@ -1872,6 +1872,102 @@ a.j13-mention-token:hover {
     }
   }
 
+  /* 内容管理工具条：类型 / 状态 / 搜索同一行，避免三行左对齐或等分顶栏留白 */
+  .admin-content-toolbar {
+    display: flex;
+    flex-wrap: wrap;
+    align-items: center;
+    gap: 0.75rem 1rem;
+    padding: 0.75rem 1rem;
+    border-bottom: 1px solid var(--line);
+    background: var(--panel);
+  }
+  @media (min-width: 640px) {
+    .admin-content-toolbar {
+      padding: 0.75rem 1.25rem;
+    }
+  }
+  .admin-content-kind {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.2rem;
+    padding: 0.2rem;
+    border-radius: 999px;
+    background: var(--panel-2);
+    flex-shrink: 0;
+  }
+  .admin-content-kind-btn {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.375rem;
+    padding: 0.4rem 0.8rem;
+    border: none;
+    border-radius: 999px;
+    background: transparent;
+    color: var(--ink-3);
+    font-size: 13px;
+    font-weight: 600;
+    line-height: 1.3;
+    cursor: pointer;
+    transition: background 0.15s ease, color 0.15s ease;
+  }
+  .admin-content-kind-btn:hover:not([aria-selected="true"]) {
+    color: var(--ink);
+  }
+  .admin-content-kind-btn[aria-selected="true"] {
+    background: var(--panel);
+    color: var(--ink);
+    box-shadow: 0 0 0 1px var(--line);
+  }
+  .admin-content-kind-btn:focus-visible {
+    outline: 2px solid var(--accent);
+    outline-offset: 2px;
+  }
+  .admin-content-kind-count {
+    min-width: 1.15rem;
+    padding: 0 0.35rem;
+    border-radius: 999px;
+    font-size: 11px;
+    font-weight: 500;
+    font-variant-numeric: tabular-nums;
+    line-height: 1.65;
+    background: var(--panel);
+    color: var(--ink-3);
+  }
+  .admin-content-kind-btn[aria-selected="true"] .admin-content-kind-count {
+    background: var(--accent-soft);
+    color: var(--accent);
+  }
+  .admin-content-split {
+    display: none;
+    width: 1px;
+    height: 1.5rem;
+    background: var(--line);
+    flex-shrink: 0;
+  }
+  .admin-content-status {
+    flex: 1 1 14rem;
+    min-width: 0;
+  }
+  .admin-content-search {
+    flex: 1 1 12rem;
+    max-width: 18rem;
+    min-width: 11rem;
+    margin-left: auto;
+  }
+  @media (min-width: 768px) {
+    .admin-content-split {
+      display: block;
+    }
+  }
+  @media (max-width: 767px) {
+    .admin-content-search {
+      flex-basis: 100%;
+      max-width: none;
+      margin-left: 0;
+    }
+  }
+
   /* ----- 点赞按钮：未赞描边态，hover 同色系填充；已赞为浅底实心态 ----- */
   .j13-like {
     border-color: var(--line-2);