fix(pricing): show dynamic rates in model picker info text

[Vizards]

Summary

• Replace legacy inputCost / outputCost / cacheCost metadata with the model picker's dynamic infoText pricing notice.
• Show the official DeepSeek peak/off-peak period, remaining duration, and per-token pricing in the configured locale.
• Restrict the pricing notice to the official DeepSeek API base URL.
• Move pricing transition refresh scheduling into PricingRefreshScheduler.

Related issue

Related to #185

Validation

• npm run format:check
• npm run compile
• npm run lint
• Manual bilingual pricing, endpoint-gating, and schedule assertions