feat: add independent load_factor field for scheduling load calculation

frontend/src/i18n/locales/en.ts

@@ -1991,10 +1991,12 @@ export default {
       proxy: 'Proxy',
       noProxy: 'No Proxy',
       concurrency: 'Concurrency',
+      loadFactor: 'Load Factor',
+      loadFactorHint: 'Defaults to concurrency',
       priority: 'Priority',
       priorityHint: 'Lower value accounts are used first',
       billingRateMultiplier: 'Billing Rate Multiplier',
-      billingRateMultiplierHint: '>=0, 0 means free. Affects account billing only',
+      billingRateMultiplierHint: '0 = free, affects account billing only',
       expiresAt: 'Expires At',
       expiresAtHint: 'Leave empty for no expiration',
       higherPriorityFirst: 'Lower value means higher priority',

frontend/src/i18n/locales/zh.ts

@@ -2133,10 +2133,12 @@ export default {
       proxy: '代理',
       noProxy: '无代理',
       concurrency: '并发数',
+      loadFactor: '负载因子',
+      loadFactorHint: '不填则等于并发数',
       priority: '优先级',
       priorityHint: '优先级越小的账号优先使用',
       billingRateMultiplier: '账号计费倍率',
-      billingRateMultiplierHint: '>=0，0 表示该账号计费为 0；仅影响账号计费口径',
+      billingRateMultiplierHint: '0 表示不计费，仅影响账号计费',
       expiresAt: '过期时间',
       expiresAtHint: '留空表示不过期',
       higherPriorityFirst: '数值越小优先级越高',