chore: add PR labeler workflow

[Pratikshya32]

Problem

Pull requests are raised without automated labels, requiring maintainers to manually categorize them based on the files touched.

Proposed Solution

Add a .github/workflows/labeler.yml workflow that automatically tags PRs with relevant labels depending on the files changed in the pull request.

[Pratikshya32]

Hello! I would like to contribute to this project. Could you please assign this issue to me and add the 'critical' label under GSSoC 2026? Thank you!