fix(a11y): ensure productivity level badge is screen-reader accessible (#952)

[mallya-m]

Summary

Fixes color-only encoding accessibility violation in CodingActivityInsightsCard productivity badge.

Closes #952

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Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor / code cleanup

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Changes Made

• Added optional ariaLabel prop to the InsightRow component
• Added aria-label="Productivity level: <Level>" to the productivity badge <p> tag so screen readers announce the level in plain English instead of the emoji name
• Added explicit TypeScript type annotation to insightRows array to support the optional ariaLabel field
• Emoji remains as a supplementary visual indicator — text label is now confirmed as the primary encoding, satisfying WCAG 2.1 SC 1.4.1

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How to Test

1. Open the dashboard Coding Activity Insights card
2. Inspect the Productivity row in browser DevTools → Accessibility tree
3. Confirm the <p> element announces "Productivity level: Excellent" (or whichever level applies) — not "large green circle Excellent"
4. Confirm the text label (Excellent, Good, Moderate, etc.) is always visible regardless of color perception

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Screenshots (if UI change)

N/A — no visual change. The fix is in the accessibility tree only.

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Checklist

• Linked issue in summary
• npm run lint passes locally
• No TypeScript errors in changed file (npx tsc --noEmit 2>&1 | Select-String "CodingActivityInsightsCard" → blank)
• Self-reviewed the diff
• Added/updated tests if applicable

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Accessibility Checklist

• aria-label added to productivity badge for screen reader support
• Color is supplementary only — text label carries the meaning (WCAG SC 1.4.1)
• Emoji marked as decorative via accessible label on parent element
• Responsive UI unaffected — no layout changes

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Additional Notes

Pre-existing build errors exist in upstream/main unrelated to this PR (@/lib/leaderboard, session.error type mismatch in repos route) — introduced by other open PRs with zero overlap with this change. Only CodingActivityInsightsCard.tsx was modified.

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