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/index.css

@@ -337,6 +337,14 @@
     font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Noto Sans SC', sans-serif;
     transition: background-color 0.3s ease, color 0.3s ease;
   }
+
+  /* Fix: Radix Dialog scroll-lock adds padding-right to body, causing white bar.
+     Override to prevent layout shift when dialog opens. */
+  body[data-scroll-locked],
+  body[data-radix-scroll-locked],
+  body[style*="padding-right"] {
+    padding-right: 0 !important;
+  }
   code, pre, .font-mono {
     font-family: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
   }