perf: use LazyWidget for below-the-fold dashboard widgets (closes #2408)

[Rudrasamadhiya]

Summary

LazyWidget was built to defer below-the-fold widget rendering via IntersectionObserver, but was never used in DashboardWidgets.tsx. This PR wires it in for the 3 rows of widgets that are below the fold (IssueMetrics, PinnedRepos, TopRepos, LanguageBreakdown, GoalTracker), so their API requests are only fired when the user scrolls near them.

Closes #2408

Changes

• Added import LazyWidget from "@/components/LazyWidget" and import Skeleton from "@/components/Skeleton"
• • Wrapped Row 3, Row 4, and Row 5 widgets in <LazyWidget fallback={<Skeleton />}>
• • Rows 1 and 2 remain eager-loaded (above the fold)

Type of Change

• Performance improvement

[github-actions]

GSSoC Label Checklist 🏷️

@Umbrella-io — please apply the appropriate labels before merging:

Difficulty (pick one):

• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

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• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

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Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus

[Priyanshu-byte-coder]

This PR has merge conflicts with the current main branch. Please rebase or merge main into your branch to resolve the conflicts, then push the updated branch. Once conflicts are resolved, this PR will be merged.

git fetch origin main
git merge origin/main
# resolve conflicts
git push

[Priyanshu-byte-coder]

This PR has merge conflicts with main. Please rebase or resolve conflicts and push again.