[BUG] No search on Leaderboard

[pericharlabindhumadhavi-data]

🐛 Bug Description

src/pages/Leaderboard.tsx only supports filtering by time range (today / week / all). There is no way to search for a specific user, so finding your own rank or a friend's rank in a large leaderboard is not possible without scrolling through the entire list.

🔄 Steps to Reproduce

1. Go to: /leaderboard
2. Click on: Try to find a specific user by name
3. Expected Outcome: A search box should let you filter/find a user by username.
4. Actual Outcome: No search input exists only the today/week/all filter tabs.

✅ Expected Behavior

Add a search input that filters the visible leaderboard entries by username (and ideally highlights/scrolls to the current logged-in user's row).

📸 Screenshots (if applicable)

N/A

🛠️ Possible Fix (if known)

Add a controlled search input above the leaderboard list, filter the existing fetched entries client-side (or add a query param for server-side search if the leaderboard is large/paginated).

📌 System Information

• Operating System: Any
• Browser/Device: Any

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GSSoC'26