pricing drift --apply should recalculate historical costs in DB

[nujovich]

Problem

When hermes telemetry pricing drift --apply updates pricing.yaml with corrected prices, historical costs in the telemetry DB remain frozen with old (higher) prices. The dashboard mixes old-price and new-price costs, making budget tracking unreliable.

Real-world example

Model	Old price	New price
moonshotai/kimi-k2.6	$0.66/$3.41	$0.5472/$2.736
deepseek-v4-pro	$0.435/$0.87	$0.348/$0.696

• Cron session with 4.9M tokens: dashboard shows $3.78, real cost ~$3.25 (−14%)
• Telegram session with 460K tokens: dashboard shows $0.30, real cost ~$0.19 (−37%)

Suggested behavior

After pricing drift --apply, recalculate cost_usd in llm_calls for rows where estimated=0 and provider_assumed=0 (they had explicit pricing at the old rate). Could be a --recalculate flag or a separate pricing recalculate subcommand.