feat(ops): add ignore insufficient balance errors toggle and extract error constants

- Add 5th error filter switch IgnoreInsufficientBalanceErrors to suppress
  upstream insufficient balance / insufficient_quota errors from ops log
- Extract hardcoded error strings into package-level constants for
  shouldSkipOpsErrorLog, normalizeOpsErrorType, classifyOpsPhase, and
  classifyOpsIsBusinessLimited
- Define ErrNoAvailableAccounts sentinel error and replace all
  errors.New("no available accounts") call sites
- Update tests to use require.ErrorIs with the sentinel error

frontend/src/api/admin/ops.ts

@@ -841,6 +841,7 @@ export interface OpsAdvancedSettings {
   ignore_context_canceled: boolean
   ignore_no_available_accounts: boolean
   ignore_invalid_api_key_errors: boolean
+  ignore_insufficient_balance_errors: boolean
   display_openai_token_stats: boolean
   display_alert_events: boolean
   auto_refresh_enabled: boolean

frontend/src/i18n/locales/en.ts

@@ -3842,6 +3842,8 @@ export default {
         ignoreNoAvailableAccountsHint: 'When enabled, "No available accounts" errors will not be written to the error log (not recommended; usually a config issue).',
         ignoreInvalidApiKeyErrors: 'Ignore invalid API key errors',
         ignoreInvalidApiKeyErrorsHint: 'When enabled, invalid or missing API key errors (INVALID_API_KEY, API_KEY_REQUIRED) will not be written to the error log.',
+        ignoreInsufficientBalanceErrors: 'Ignore Insufficient Balance Errors',
+        ignoreInsufficientBalanceErrorsHint: 'When enabled, upstream insufficient account balance errors will not be written to the error log.',
         autoRefresh: 'Auto Refresh',
         enableAutoRefresh: 'Enable auto refresh',
         enableAutoRefreshHint: 'Automatically refresh dashboard data at a fixed interval.',

frontend/src/i18n/locales/zh.ts

@@ -4016,6 +4016,8 @@ export default {
         ignoreNoAvailableAccountsHint: '启用后，"No available accounts" 错误将不会写入错误日志（不推荐，这通常是配置问题）。',
         ignoreInvalidApiKeyErrors: '忽略无效 API Key 错误',
         ignoreInvalidApiKeyErrorsHint: '启用后，无效或缺失 API Key 的错误（INVALID_API_KEY、API_KEY_REQUIRED）将不会写入错误日志。',
+        ignoreInsufficientBalanceErrors: '忽略余额不足错误',
+        ignoreInsufficientBalanceErrorsHint: '启用后，上游账号余额不足（Insufficient balance）的错误将不会写入错误日志。',
         autoRefresh: '自动刷新',
         enableAutoRefresh: '启用自动刷新',
         enableAutoRefreshHint: '自动刷新仪表板数据，启用后会定期拉取最新数据。',

frontend/src/views/admin/ops/components/OpsSettingsDialog.vue

@@ -516,6 +516,16 @@ async function saveAllSettings() {
               </div>
               <Toggle v-model="advancedSettings.ignore_invalid_api_key_errors" />
             </div>
+
+            <div class="flex items-center justify-between">
+              <div>
+                <label class="text-sm font-medium text-gray-700 dark:text-gray-300">{{ t('admin.ops.settings.ignoreInsufficientBalanceErrors') }}</label>
+                <p class="mt-1 text-xs text-gray-500">
+                  {{ t('admin.ops.settings.ignoreInsufficientBalanceErrorsHint') }}
+                </p>
+              </div>
+              <Toggle v-model="advancedSettings.ignore_insufficient_balance_errors" />
+            </div>
           </div>
 
           <!-- Auto Refresh -->