Perf/memoize pinned top repos 1458

[Antra1705]

Summary

Refined the custom comparator for the memoized RepoItem component in TopRepos.tsx to fix missing equality checks that caused stale UI states during real-time SSE sync events.

Closes #1458

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Type of Change

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

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Changes Made

• Added shallow equality checks on repo.url and repo.description in the RepoItem comparator
• Added deep equality check on repo.languages array to prevent stale language badges
• Added deep equality check on health.signals to prevent stale health tooltips
• Extracted helper functions areLanguagesEqual and areHealthSignalsEqual to keep comparator logic self-contained

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How to Test

1. Run npm run dev and open the dashboard
2. Open React DevTools Profiler and record while typing in the search bar or switching account contexts
3. Verify that RepoItem components with unchanged data do not re-render

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Screenshots (if UI change)

N/A

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Checklist

• Linked issue in summary
• npm run lint passes locally
• No TypeScript errors (npm run type-check)
• npm run build succeeds
• Self-reviewed the diff
• Added/updated tests if applicable

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Additional Notes

Core React.memo wrappers for RepoItem and RepoCard were introduced in PR #1503. This PR refines the comparator logic only — no structural changes to component hierarchy.

The failing E2E check (streak freeze API in e2e/streak.spec.ts:229) is unrelated to this PR's changes, which are scoped to TopRepos.tsx only. Confirmed pre-existing on main — caused by setupStreakMocks returning an empty contributions object, triggering an early return in StreakTracker.tsx before the freeze button renders.

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