fix(account): prevent quota-exceeded API key/Bedrock accounts from being scheduled

Add quota exceeded check to IsSchedulable() and refactor
shouldClearStickySession to delegate to IsSchedulable(), eliminating
duplicated logic and fixing missed overload/rate-limit/expired checks.
Frontend displays quota exceeded status independently via quota fields.

frontend/src/i18n/locales/zh.ts

@@ -2315,6 +2315,7 @@ export default {
         rateLimited: '限流中',
         overloaded: '过载中',
         tempUnschedulable: '临时不可调度',
+        quotaExceeded: '配额超限',
         unschedulable: '不可调度',
         rateLimitedUntil: '限流中，当前不参与调度，预计 {time} 自动恢复',
         rateLimitedAutoResume: '{time} 自动恢复',