feat(usage): plan:kimi_coding 兼容 kimi-code 0.43.1 quota 用量模型

服务端 api.kimi.com/coding/v1/usages 已由绝对 used/limit 行切换为
quota 模型（usages.limit_5h/limit_7d/limit_month_total/limit_month_code，
条目为 used_ratio 0-1 比率 + reset_time），见上游 #3787。

- parse_kimi_coding 优先解析新结构，旧 limits/usage 结构保留为回退
- used_ratio >1 时按已是百分数处理（防御）
- 新 tier id month_code + 前端 planLabel/i18n 中英文案
- 新增 3 个测试：四窗口解析 / 比率防御 / 空窗口回退旧结构

src/i18n/en.ts

@@ -449,6 +449,7 @@ export const enTranslations: Record<TranslationKey, string> = {
   usageTierDaily: "Daily",
   usageTierWeekly: "Weekly",
   usageTierMonthly: "Monthly",
+  usageTierMonthCode: "Monthly (code)",
   usageErrNoKey: "No API key configured",
   usageErrDisabled: "Usage query is disabled in the config panel",
   usageErrLoginExpired: "Kimi Code login expired and auto-refresh failed; run `kimi login` again",