fix(usage): 显示缓存 Token 明细

[SavitarC]

Summary

• Extend admin usage stats response typing with cache creation/read token fields.
• Show cache tokens in the Total Tokens card alongside input/output tokens.
• Add a cache token tooltip with creation/read breakdown values.
• Add English and Chinese locale entries for the cache token labels.
• Add a component test covering cache total and breakdown rendering.

Validation

• npm --prefix frontend run test:run -- src/components/admin/usage/__tests__/UsageStatsCards.spec.ts
• npm --prefix frontend run typecheck
• git diff --check origin/main...HEAD

[github-actions]

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[SavitarC]

I have read the CLA Document and I hereby sign the CLA