Add PR count on issue cards in contribute page

Community & Support: [LinkedIn Group](https://www.linkedin.com/groups/14656108/) · [Slack #project-nest](https://owasp.slack.com/archives/project-nest)

Active project leaders: Arkadii Yakovets -- [GitHub](https://github.com/arkid15r/) · [LinkedIn](https://www.linkedin.com/in/arkid15r/) · [Slack](https://owasp.slack.com/team/U060W3NKLTF); Kate Golovanova -- [GitHub](https://github.com/kasya/) · [LinkedIn](https://www.linkedin.com/in/kate-golovanova/) · [Slack](https://owasp.slack.com/team/U07PWB1JZ6Z)

[Contributing](https://github.com/owasp/nest/blob/main/CONTRIBUTING.md) · [Code of Conduct](https://github.com/owasp/nest/blob/main/CODE_OF_CONDUCT.md) · [GSoC Mentors](https://github.com/owasp/nest/blob/main/MENTORS.md)

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**Is your feature request related to a problem? Please describe.**
Currently, issue cards on the Contribute page do not show how many open pull requests exist for each issue, making it difficult for contributors to tell whether an issue is already being actively worked on without clicking through to GitHub.

**Describe the solution you'd like**
Add an open pull request count indicator to each issue card on the Contribute page. The pullRequests field is already available in the existing Issue type and Algolia indexed data(making this a purely frontend change).

**Describe alternatives you've considered**
An alternative would be to add an "assigned" or "in progress" label to issues, however this would require maintainers to manually update labels. Showing PR count is more accurate and automatically reflects the current state.
**Are you going to work on implementing this?**

- [x] Yes
- [] No

**Additional context**
This improvement would make the contributor experience significantly smoother by surfacing key information directly on the card, reducing unnecessary clicks and helping contributors find truly available issues faster.