[FEAT] Add Reusable Empty State Components for Dashboard Widgets #2646

[desireddymohithreddy0925]

Summary

Creates a unified, reusable EmptyState component to replace blank sections across dashboard widgets, improving user guidance when data is unavailable.

Closes #2646

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that changes existing behavior)
• 📝 Documentation update
• ♻️ Refactor / code cleanup (no functional change)
• ⚡ Performance improvement
• 🔒 Security fix
• 🧪 Tests only

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What Changed

• Built a generic EmptyState component supporting custom icons, titles, descriptions, and action buttons.
• Replaced the inconsistent blank states in src/components/TopRepos.tsx (Repositories Widget) and src/components/PRMetrics.tsx (PR Analytics Widget).
• Updated existing empty states in src/components/GoalTracker.tsx (Goals Widget) and src/app/leaderboard/page.tsx (Leaderboard Widget) to match the standardized phrasing and action labels requested.
• Ensured responsiveness and support for both light/dark themes.

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How to Test

1. Navigate to the dashboard using a fresh test account with 0 repositories, 0 PRs, and 0 goals.
2. Verify the Goals Widget displays "No goals created yet" with a "Create Goal" button.
3. Verify the Top Repositories Widget displays "No repositories found" with a "Refresh Data" button.
4. Verify the PR Analytics Widget displays "No pull requests available" with a "View GitHub Profile" button.
5. Navigate to the Leaderboard and verify it displays "No leaderboard data available" with a "Sync Dashboard" button.

Expected result: All widgets should now display the new, consistent EmptyState component rather than blank space or unstyled text.

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Screenshots / Recordings

Before	After
(Blank spaces or basic text)	(Consistent EmptyState components with icons and buttons)

[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — 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

Quality (optional):

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

Validation (required to score):

• gssoc:approved — counts for points
• gssoc:invalid / gssoc:spam / gssoc:ai-slop — does not score

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