feat: 改进管理界面弹窗体验和滚动条美化

- 修复API Key创建/编辑弹窗和账户信息修改弹窗在低高度屏幕上被遮挡的问题
- 为所有弹窗添加自适应高度支持，最大高度限制为90vh
- 美化Claude账户弹窗的滚动条样式，使用紫蓝渐变色与主题保持一致
- 添加响应式适配，移动设备上弹窗高度调整为85vh
- 优化滚动条交互体验，支持悬停和激活状态

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

web/admin/style.css

@@ -378,6 +378,43 @@ body::before {
 
 
 
+/* 自定义滚动条样式 */
+.custom-scrollbar {
+    scrollbar-width: thin;
+    scrollbar-color: rgba(102, 126, 234, 0.3) rgba(102, 126, 234, 0.05);
+}
+
+.custom-scrollbar::-webkit-scrollbar {
+    width: 8px;
+    height: 8px;
+}
+
+.custom-scrollbar::-webkit-scrollbar-track {
+    background: rgba(102, 126, 234, 0.05);
+    border-radius: 10px;
+}
+
+.custom-scrollbar::-webkit-scrollbar-thumb {
+    background: linear-gradient(135deg, rgba(102, 126, 234, 0.4) 0%, rgba(118, 75, 162, 0.4) 100%);
+    border-radius: 10px;
+    transition: background 0.3s ease;
+}
+
+.custom-scrollbar::-webkit-scrollbar-thumb:hover {
+    background: linear-gradient(135deg, rgba(102, 126, 234, 0.6) 0%, rgba(118, 75, 162, 0.6) 100%);
+}
+
+.custom-scrollbar::-webkit-scrollbar-thumb:active {
+    background: linear-gradient(135deg, rgba(102, 126, 234, 0.8) 0%, rgba(118, 75, 162, 0.8) 100%);
+}
+
+/* 弹窗滚动内容样式 */
+.modal-scroll-content {
+    max-height: calc(90vh - 160px);
+    overflow-y: auto;
+    padding-right: 8px;
+}
+
 @media (max-width: 768px) {
     .glass, .glass-strong {
         margin: 16px;
@@ -392,4 +429,8 @@ body::before {
         font-size: 14px;
         padding: 12px 8px;
     }
+    
+    .modal-scroll-content {
+        max-height: calc(85vh - 120px);
+    }
 }