fix(miners): align per-repository standings table headers at responsive breakpoints

[carlh7777]

Summary

Fixes responsive layout issues in the Per-repository standings table on the Miner Details page where headers could become misaligned, truncated, or overflow outside the standings card at medium viewport widths.

Changes

• Constrain the shared DataTable scroll container so tables remain contained within their parent layout and scroll horizontally when necessary
• Replace percentage-based column widths in MinerRepoStandings with fixed widths to maintain header alignment
• Add right-aligned sortable header styling for numeric columns
• Prevent the standings table from overflowing into the identity sidebar
• Add table minimum widths to preserve single-line headers and consistent column sizing
• Preserve existing sorting behavior and interactions

Related Issues

Fixes #1329

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (describe below)

Screenshots

Before

After

Checklist

• New components are modularized/separated where sensible
• Uses predefined theme (e.g. no hardcoded colors)
• Responsive/mobile checked
• Tested against the test API
• npm run format and npm run lint:fix have been run
• npm run build passes
• Screenshots included for any UI/visual changes