Fixed bug in the 24h activity tile for all nodes table

[javuto]

Summary

• Fixed the all-nodes 24h activity column so it loads enough Redis-backed activity data across UTC midnight.
• Updated the node activity heatmap to render exactly the trailing 24 hourly buckets.
• Added regression coverage for:
  • Fetching two Redis day blobs for the all-nodes 24h activity column.
  • Rendering a fixed 24-hour heatmap from two-day activity data.

Validation

• npm test -- NodesTablePage.test.tsx
• npm run check
• git diff --check