fix: validate account status before update and update load factor hint

- Normalize non-standard status (e.g. "error") to "active" on edit load
- Add pre-submit validation for status field to prevent 400 errors
- Update load factor hint: "提高负载因子可以提高对账号的调度频率"

frontend/src/i18n/locales/en.ts

@@ -1992,7 +1992,7 @@ export default {
       noProxy: 'No Proxy',
       concurrency: 'Concurrency',
       loadFactor: 'Load Factor',
-      loadFactorHint: 'Defaults to concurrency',
+      loadFactorHint: 'Higher load factor increases scheduling frequency',
       priority: 'Priority',
       priorityHint: 'Lower value accounts are used first',
       billingRateMultiplier: 'Billing Rate Multiplier',
@@ -2012,6 +2012,7 @@ export default {
       accountUpdated: 'Account updated successfully',
       failedToCreate: 'Failed to create account',
       failedToUpdate: 'Failed to update account',
+      pleaseSelectStatus: 'Please select a valid account status',
       mixedChannelWarningTitle: 'Mixed Channel Warning',
       mixedChannelWarning: 'Warning: Group "{groupName}" contains both {currentPlatform} and {otherPlatform} accounts. Mixing different channels may cause thinking block signature validation issues, which will fallback to non-thinking mode. Are you sure you want to continue?',
       pleaseEnterAccountName: 'Please enter account name',

frontend/src/i18n/locales/zh.ts

@@ -2134,7 +2134,7 @@ export default {
       noProxy: '无代理',
       concurrency: '并发数',
       loadFactor: '负载因子',
-      loadFactorHint: '不填则等于并发数',
+      loadFactorHint: '提高负载因子可以提高对账号的调度频率',
       priority: '优先级',
       priorityHint: '优先级越小的账号优先使用',
       billingRateMultiplier: '账号计费倍率',
@@ -2154,6 +2154,7 @@ export default {
       accountUpdated: '账号更新成功',
       failedToCreate: '创建账号失败',
       failedToUpdate: '更新账号失败',
+      pleaseSelectStatus: '请选择有效的账号状态',
       mixedChannelWarningTitle: '混合渠道警告',
       mixedChannelWarning: '警告：分组 "{groupName}" 中同时包含 {currentPlatform} 和 {otherPlatform} 账号。混合使用不同渠道可能导致 thinking block 签名验证问题，会自动回退到非 thinking 模式。确定要继续吗？',
       pleaseEnterAccountName: '请输入账号名称',