📱 refactor(web): remove legacy isMobile util and migrate to useIsMobile hook

BREAKING CHANGE:
helpers/utils.js no longer exports `isMobile()`.
Any external code that relied on this function must switch to the `useIsMobile` React hook.

Summary
-------
1. Deleted the obsolete `isMobile()` function from helpers/utils.js.
2. Introduced `MOBILE_BREAKPOINT` constant and `matchMedia`-based detection for non-React contexts.
3. Reworked toast positioning logic in utils.js to rely on `matchMedia`.
4. Updated render.js:
   • Removed isMobile import.
   • Added MOBILE_BREAKPOINT detection in `truncateText`.
5. Migrated every page/component to the `useIsMobile` hook:
   • Layout: HeaderBar, PageLayout, SiderBar
   • Pages: Home, Detail, Playground, User (Add/Edit), Token, Channel, Redemption, Ratio Sync
   • Components: ChannelsTable, ChannelSelectorModal, ConflictConfirmModal
6. Purged all remaining `isMobile()` calls and legacy imports.
7. Added missing `const isMobile = useIsMobile()` declarations where required.

Benefits
--------
• Unifies mobile detection with a React-friendly hook.
• Eliminates duplicated logic and improves maintainability.
• Keeps non-React helpers lightweight by using `matchMedia` directly.

web/src/helpers/utils.js

@@ -4,6 +4,7 @@ import React from 'react';
 import { toast } from 'react-toastify';
 import { THINK_TAG_REGEX, MESSAGE_ROLES } from '../constants/playground.constants';
 import { TABLE_COMPACT_MODES_KEY } from '../constants';
+import { MOBILE_BREAKPOINT } from '../hooks/useIsMobile.js';
 
 const HTMLToastContent = ({ htmlContent }) => {
   return <div dangerouslySetInnerHTML={{ __html: htmlContent }} />;
@@ -67,9 +68,7 @@ export async function copy(text) {
   return okay;
 }
 
-export function isMobile() {
-  return window.innerWidth <= 600;
-}
+// isMobile 函数已移除，请改用 useIsMobile Hook
 
 let showErrorOptions = { autoClose: toastConstants.ERROR_TIMEOUT };
 let showWarningOptions = { autoClose: toastConstants.WARNING_TIMEOUT };
@@ -77,7 +76,8 @@ let showSuccessOptions = { autoClose: toastConstants.SUCCESS_TIMEOUT };
 let showInfoOptions = { autoClose: toastConstants.INFO_TIMEOUT };
 let showNoticeOptions = { autoClose: false };
 
-if (isMobile()) {
+const isMobileScreen = window.matchMedia(`(max-width: ${MOBILE_BREAKPOINT - 1}px)`).matches;
+if (isMobileScreen) {
   showErrorOptions.position = 'top-center';
   // showErrorOptions.transition = 'flip';