feat: add fiat price overlay and price impact analysis

[twirtle2]

Summary

This PR introduces the fiat price overlay / price impact feature for node rewards, adding historical daily close pricing context to reward analytics and charts.

What this feature adds

• Price impact analytics that compare reward value at receipt vs value at today’s price
• Reward scatter visualization colored by USD value at receipt
• Supporting data pipeline for daily ALGO close history used by the charts
• Hook/data plumbing and tests for date bucketing + price-availability behavior

How it works

• Reward blocks are grouped by UTC date.
• Each day is joined with the corresponding daily ALGO close from algo-price-history.json.
• Price-impact charts use this joined dataset to compute:
  • value at receipt (daily close on reward day)
  • value at today’s price (current ticker)
  • cumulative comparisons over time
• Scatter points are intentionally shown only when closed daily price data exists (rewardAlgo > 0 && valueAtReceipt !== null).

Included refinement in this PR

To make feature behavior consistent with UTC day boundaries, this PR also includes:

• scheduled price-history update moved from 06:00 UTC to 00:00 UTC
• chart copy clarifying why the current UTC day can appear after the next refresh

Validation

• npm run test
• npm run lint
• npm run build

Preview

• https://feat-fiat-price-overlay-algonoderewards.twirtle2.workers.dev/