feat: 钱包类型枚举与前端账号类型展示

后端：
- 新增 WalletType 枚举（MAGIC/SAFE），移除 safe/magic 字符串硬编码
- RelayClientService/BlockchainService/AccountService/OrderSigningService 使用枚举
- Builder Relayer API 类型使用常量 RELAYER_TYPE_PROXY/SAFE

前端：
- 账户列表、详情、导入 Modal 显示账号类型（Magic/Safe Tag）
- 导入账户 Modal 移除安全提示 Alert，移除 showAlert 与相关 i18n
- 移除无用 i18n key：securityTip、securityTipDesc、walletTypeMagic、walletTypeSafe、magicNotSupported
- 钱包类型 Tag 简化为仅显示 Magic 或 Safe

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/locales/en/common.json

@@ -53,6 +53,7 @@
     "accountId": "Account ID",
     "accountName": "Account Name",
     "walletAddress": "Wallet Address",
+    "walletType": "Wallet Type",
     "balance": "Account Balance",
     "refreshBalance": "Refresh Balance",
     "apiCredentials": "API Credentials Configuration",
@@ -122,6 +123,7 @@
     "importAccount": "Import Account",
     "accountName": "Account Name",
     "walletAddress": "Wallet Address",
+    "walletType": "Wallet Type",
     "proxyAddress": "Proxy Wallet Address",
     "apiCredentials": "API Credentials",
     "balance": "Balance",
@@ -178,8 +180,6 @@
   "accountImport": {
     "title": "Import Account",
     "back": "Back",
-    "securityTip": "Security Tip",
-    "securityTipDesc": "Private keys will be stored in the backend database. Please ensure database access is secure. HTTPS is recommended.",
     "importMethod": "Import Method",
     "privateKey": "Private Key",
     "mnemonic": "Mnemonic",
@@ -213,9 +213,6 @@
     "addressErrorMnemonic": "Cannot derive address from mnemonic",
     "walletType": "Wallet Type",
     "walletTypeHelp": "Web3 Wallet: Polymarket accounts connected via browser wallets like MetaMask\nMagic: Polymarket accounts logged in via email or social accounts (Google, Twitter, etc.)",
-    "walletTypeMagic": "Magic (Email/Social Login)",
-    "walletTypeSafe": "Web3 Wallet",
-    "magicNotSupported": "",
     "loadingProxyOptions": "Loading proxy addresses and asset information...",
     "selectProxyOption": "Please select a proxy address",
     "proxyOptionRequired": "Please select a proxy address",