feat(web): 页脚品牌与备案信息、首页文案精简及导航/侧栏交互优化

- 页脚「纯文本驱动」改为 Powered by Pure Note（链至仓库地址），新增
  公安备案展示：国徽图标 + 备案号链至 beian.mps.gov.cn，备案号可在
  后台设置（站点描述下一项）配置，留空不显示
- settings 白名单新增 beian_no 键（trim、≤200 字符、可清空），/api/site
  一并下发；TestSettingsWhitelist 补生效/清空/超长用例
- 去除首页 hero 文案区（PURE NOTE · 极简笔记/记录，而不打扰。等），
  同步清理失效样式并微调顶部留白
- 博客 header 首页/标签菜单补 House/Tags 图标，与管理按钮同风格
- 管理侧栏「返回博客/退出登录」浓缩为图标按钮置于用户行右侧，CSS
  悬浮 tooltip（top-center、带箭头，原生 title 延迟高不采用），返回
  博客改新窗口打开

web/src/index.css

@@ -517,6 +517,24 @@ button:focus-visible {
 .pn-site-footer-inner a:hover {
   color: var(--foreground);
 }
+.pn-site-footer-line {
+  margin: 0;
+}
+.pn-site-beian {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  margin-top: 8px;
+}
+.pn-site-beian img {
+  width: 14px;
+  height: 14px;
+  flex: none;
+  opacity: 0.85;
+}
+.pn-site-beian:hover img {
+  opacity: 1;
+}
 
 @media (max-width: 640px) {
   .pn-site-header-inner {
@@ -535,35 +553,9 @@ button:focus-visible {
    首页（博客首页.html）
    ============================================================ */
 .pn-home-content {
-  padding-top: 64px;
+  padding-top: 56px;
   padding-bottom: 24px;
 }
-.pn-home-hero {
-  margin-bottom: 48px;
-}
-.pn-home-eyebrow {
-  margin: 0 0 18px;
-  font-family: var(--font-mono);
-  font-size: 12px;
-  letter-spacing: 0.14em;
-  color: var(--muted-foreground);
-}
-.pn-home-title {
-  margin: 0 0 18px;
-  font-family: var(--font-serif);
-  font-weight: 400;
-  font-size: clamp(34px, 6vw, 46px);
-  line-height: 1.18;
-  letter-spacing: var(--tracking-tight);
-  color: var(--foreground);
-}
-.pn-home-desc {
-  margin: 0;
-  max-width: 560px;
-  font-size: 15px;
-  line-height: 1.8;
-  color: var(--muted-foreground);
-}
 .pn-home-filter {
   margin-bottom: 8px;
 }
@@ -728,10 +720,7 @@ button:focus-visible {
 }
 @media (max-width: 640px) {
   .pn-home-content {
-    padding-top: 44px;
-  }
-  .pn-home-hero {
-    margin-bottom: 40px;
+    padding-top: 40px;
   }
   .pn-home-post {
     padding: 26px 0;
@@ -1597,6 +1586,78 @@ button:focus-visible {
   gap: 10px;
   padding: 8px 10px 2px;
 }
+.pn-admin-user-actions {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  margin-left: auto;
+}
+.pn-admin-iconbtn {
+  position: relative;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 28px;
+  height: 28px;
+  padding: 0;
+  border: 0;
+  border-radius: var(--radius-sm);
+  background: transparent;
+  color: var(--muted-foreground);
+  text-decoration: none;
+  cursor: pointer;
+  transition: background-color 0.15s ease, color 0.15s ease;
+}
+.pn-admin-iconbtn:hover {
+  background: var(--sidebar-accent);
+  color: var(--sidebar-accent-foreground);
+}
+.pn-admin-iconbtn svg {
+  width: 15px;
+  height: 15px;
+}
+/* CSS 悬浮 tooltip（原生 title 延迟高且部分环境不显示） */
+.pn-admin-iconbtn::after {
+  content: attr(data-tip);
+  position: absolute;
+  left: 50%;
+  bottom: calc(100% + 10px);
+  z-index: 30;
+  padding: 4px 8px;
+  border-radius: var(--radius-sm);
+  background: var(--primary);
+  color: var(--primary-foreground);
+  font-size: 11px;
+  font-weight: 500;
+  line-height: 1.4;
+  white-space: nowrap;
+  opacity: 0;
+  pointer-events: none;
+  transform: translate(-50%, 2px);
+  transition: opacity 0.15s ease, transform 0.15s ease;
+}
+.pn-admin-iconbtn::before {
+  content: "";
+  position: absolute;
+  left: 50%;
+  bottom: 100%;
+  z-index: 30;
+  margin-left: -5px;
+  border: 5px solid transparent;
+  border-top-color: var(--primary);
+  opacity: 0;
+  pointer-events: none;
+  transition: opacity 0.15s ease;
+}
+.pn-admin-iconbtn:hover::after,
+.pn-admin-iconbtn:focus-visible::after {
+  opacity: 1;
+  transform: translate(-50%, 0);
+}
+.pn-admin-iconbtn:hover::before,
+.pn-admin-iconbtn:focus-visible::before {
+  opacity: 1;
+}
 .pn-admin-avatar {
   width: 28px;
   height: 28px;