Add search and filter functionality for challenges

[RishabhJain2018]

Description:

To improve the usability and discoverability of challenges on the platform, we should implement a search and filter feature on the frontend challenges list page.

A starting point for this work was laid out in [PR #4175](https://github.com/Cloud-CV/EvalAI/pull/4175), which introduces a basic search capability. This can be expanded and refined to include advanced filtering options and improve the UX.

Motivation:

• As the number of hosted challenges grows, users need an efficient way to find specific challenges.
• A clean and functional UI/UX for filtering by attributes (e.g., category, status, submission type) will significantly enhance the experience for both participants and organizers.

Tasks:

• [ ] Review and build upon [PR #4175](https://github.com/Cloud-CV/EvalAI/pull/4175) (which introduced a basic search box).
• [ ] Add filters for challenge attributes (e.g., ongoing/past, evaluation type, organization, etc.).
• [ ] Integrate search and filter with existing API endpoints (or update backend endpoints if necessary).
• [ ] Ensure filters and search work together smoothly (e.g., combined filtering and keyword search).
• [ ] Make the UI responsive and accessible.

Reference:

• Initial implementation PR: [#4175](https://github.com/Cloud-CV/EvalAI/pull/4175)

[Divyanshu7001]

@RishabhJain2018 /assign