fix: 统一弹框组件 — ModalOverlay对齐EditInstanceDialog行为

- ModalOverlay移除遮罩层onClick(不响应外部点击关闭)
- 移除body.style.overflow=hidden(修复白条问题)
- max-h从90vh改为85vh(与EditInstanceDialog一致)
- 10个页面手写fixed弹框替换为ModalOverlay组件
- InstanceGroupPage/WorkflowPage/UsersPage/RedisDetailPage/TicketsPage已替换
- dialog.tsx添加onPointerDownOutside/onInteractOutside阻止外部点击
- index.css添加body[data-scroll-locked]覆盖Radix滚动锁定
- Layout.tsx main添加relative定位上下文

frontend/src/App.css

@@ -1,42 +1 @@
-#root {
-  max-width: 1280px;
-  margin: 0 auto;
-  padding: 2rem;
-  text-align: center;
-}
-
-.logo {
-  height: 6em;
-  padding: 1.5em;
-  will-change: filter;
-  transition: filter 300ms;
-}
-.logo:hover {
-  filter: drop-shadow(0 0 2em #646cffaa);
-}
-.logo.react:hover {
-  filter: drop-shadow(0 0 2em #61dafbaa);
-}
-
-@keyframes logo-spin {
-  from {
-    transform: rotate(0deg);
-  }
-  to {
-    transform: rotate(360deg);
-  }
-}
-
-@media (prefers-reduced-motion: no-preference) {
-  a:nth-of-type(2) .logo {
-    animation: logo-spin infinite 20s linear;
-  }
-}
-
-.card {
-  padding: 2em;
-}
-
-.read-the-docs {
-  color: #888;
-}
+/* App styles — Vite template defaults removed */