feat: 会员中心全局暗色主题重构

阶段一：全局覆盖
- 新增 dark-override.css (450+ 行)，覆盖所有 Element UI 组件暗色样式
  - 输入框、表格、Tabs、弹窗、按钮、分页、复选框、下拉框等
  - 侧边栏、顶栏、主内容区暗色背景
  - 滚动条、日期选择器、消息面板等
- header.php 引入 dark-override.css

阶段二：页面独立 CSS 暗色化（22 个文件）
- 白色背景 #fff → #161b22
- 浅灰背景 #F3F5F9 → #0d1117
- 深色文字 #171725/#1E2736 → #E6E8EB
- 灰色文字 #8692B0 → #8B949E
- 浅色边框 #E6E7EB → rgba(255,255,255,0.06)
- 悬停背景 #F5F7FA → #21262d

clientarea/hgcloud/css/security_ssh.css

@@ -45,7 +45,7 @@
   background: #eeeeee;
   border-radius: 3px;
   font-size: 0.13rem;
-  color: #757575;
+  color: #8B949E;
   display: flex;
   align-items: center;
   justify-content: center;
@@ -68,7 +68,7 @@
   cursor: pointer;
 }
 .main-card .create-api-dialog .dialog-main .content-msg {
-  border: 1px solid #e6e7eb;
+  border: 1px solid rgba(255,255,255,0.06);
   border-radius: 3px;
   display: flex;
   flex-direction: column;
@@ -80,7 +80,7 @@
   align-items: center;
   margin-left: 0.3rem;
   margin-top: 0.2rem;
-  color: #757575;
+  color: #8B949E;
 }
 .main-card .create-api-dialog .dialog-main .content-msg .msg-item:last-child {
   margin-bottom: 0.3rem;
@@ -115,7 +115,7 @@
 .main-card .delete-dialog .del-dialog-main {
   font-size: 0.16rem;
   font-weight: 800;
-  color: #1e2736;
+  color: #E6E8EB;
   margin-top: 0.3rem;
   margin-bottom: 0.4rem;
 }
@@ -140,7 +140,7 @@
 }
 .main-card .delete-dialog .del-dialog-footer .btn-no {
   background: #e7e7e7;
-  color: #1e2736;
+  color: #E6E8EB;
   margin-top: 0.16rem;
 }
 .main-card .white-ip-dialog .dialog-main .info-alert {
@@ -165,7 +165,7 @@
   margin-left: 1.04rem;
   margin-top: 0.2rem;
   margin-bottom: 0.3rem;
-  color: #8692b0;
+  color: #8B949E;
 }
 .main-card .white-ip-dialog .dialog-main .alert-text {
   margin-top: 0.2rem;
@@ -234,7 +234,7 @@
 }
 .dialog-main .label {
   font-size: 0.16rem;
-  color: #1e2736;
+  color: #E6E8EB;
   margin-bottom: 0.1rem;
 }
 .dialog-main .label:not(:first-child) {