feat: add projected API pricing to dashboard

[newbish]

Summary

• add projected API-priced cost alongside tracked cost in the dashboard
• refresh public pricing snapshots periodically from a public model pricing catalog and cache the results in D1
• show tracked vs projected cost in KPI, model breakdown, and cost rollup views

Validation

• npm run typecheck
• npm test -- --run src/lib/openai-usage.test.ts src/lib/token-analytics.test.ts src/lib/dashboard-timeframe.test.ts src/lib/dashboard-projects.test.ts src/lib/dashboard-agent-status.test.ts
• npm run build
• npm run cf:d1:bootstrap:local
• browser-verified overview, models, and cost tabs locally on port 3002

[github-actions]

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