修复长按消息气泡弹出自定义菜单时，浏览器/系统原生右键菜单跟着一起弹出的问题

chat-message.jsx 新增 suppressNativeContextMenu，在气泡上监听 contextmenu 事件并 preventDefault，
避免长按（或桌面端右键/触屏模拟长按）触发的原生上下文菜单和应用自己的长按菜单重叠显示。
css/base.css 给 .bubble 补了 -webkit-touch-callout:none，同时覆盖 iOS Safari 那条独立于
contextmenu 事件之外的长按呼出菜单（复制/查询/分享...），不影响 user-select，桌面端正常的
点击拖拽选字复制不受影响。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

umd/src_views_messages-view_jsx.dev.js

@@ -2718,6 +2718,7 @@ class BaseChatMessage extends (react__WEBPACK_IMPORTED_MODULE_0___default().Pure
     this.handleTouchStart = this.handleTouchStart.bind(this);
     this.handleTouchMove = this.handleTouchMove.bind(this);
     this.handleTouchEnd = this.handleTouchEnd.bind(this);
+    this.suppressNativeContextMenu = this.suppressNativeContextMenu.bind(this);
     this.handleCancelUpload = this.handleCancelUpload.bind(this);
     this.handleDraftyClick = this.handleDraftyClick.bind(this);
     this.handleVoicePlayed = this.handleVoicePlayed.bind(this);
@@ -2841,6 +2842,9 @@ class BaseChatMessage extends (react__WEBPACK_IMPORTED_MODULE_0___default().Pure
     }
     this.longPressOrigin = null;
   }
+  suppressNativeContextMenu(e) {
+    e.preventDefault();
+  }
   componentWillUnmount() {
     this.cancelLongPress();
   }
@@ -3098,6 +3102,7 @@ class BaseChatMessage extends (react__WEBPACK_IMPORTED_MODULE_0___default().Pure
           onTouchStart: this.handleTouchStart,
           onTouchMove: this.handleTouchMove,
           onTouchEnd: this.handleTouchEnd,
+          onContextMenu: this.suppressNativeContextMenu,
           children: [showVoiceUnreadDot ? (0,react_jsx_dev_runtime__WEBPACK_IMPORTED_MODULE_10__.jsxDEV)("i", {
             className: "voice-unread-dot"
           }, void 0, false) : null, (0,react_jsx_dev_runtime__WEBPACK_IMPORTED_MODULE_10__.jsxDEV)("div", {