feat: 添加交易历史、错误提示和打包优化

1. 交易历史记录功能
   - 新增 useTransactionHistory hook 管理交易记录
   - 新增 TransactionHistory 组件显示历史
   - 交易记录保存到 localStorage

2. 错误处理和用户提示
   - 新增 Toast 通知组件
   - 交易提交/成功/失败时显示提示
   - 解析并显示友好的错误信息

3. 打包优化
   - 配置代码分割 (manualChunks)
   - 分离 react/web3/walletconnect/i18n
   - 提高 chunk 大小警告阈值

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/context/TransactionContext.tsx

@@ -0,0 +1,33 @@
+import { createContext, useContext } from 'react'
+import type { ReactNode } from 'react'
+import { useTransactionHistory } from '../hooks/useTransactionHistory'
+import type { TransactionRecord, TransactionType } from '../hooks/useTransactionHistory'
+
+interface TransactionContextType {
+  transactions: TransactionRecord[]
+  addTransaction: (tx: Omit<TransactionRecord, 'id' | 'timestamp'>) => string
+  updateTransaction: (id: string, updates: Partial<TransactionRecord>) => void
+  clearHistory: () => void
+}
+
+const TransactionContext = createContext<TransactionContextType | null>(null)
+
+export function TransactionProvider({ children }: { children: ReactNode }) {
+  const history = useTransactionHistory()
+
+  return (
+    <TransactionContext.Provider value={history}>
+      {children}
+    </TransactionContext.Provider>
+  )
+}
+
+export function useTransactions() {
+  const context = useContext(TransactionContext)
+  if (!context) {
+    throw new Error('useTransactions must be used within TransactionProvider')
+  }
+  return context
+}
+
+export type { TransactionType, TransactionRecord }