Modified CI To run backend tests on pull requests

[SumitKumar777]

Description

This PR updates the backend CI workflow to ensure backend tests run on pull requests, not only after code is merged into main.

Problem

Currently, backend tests are triggered only on pushes to the main branch. As a result, pull requests can be merged without backend test coverage.

Changes

• Added a pull_request trigger to .github/workflows/backend-test.yml

• Backend tests now run for pull requests targeting main and dev

• Fixes: Chore Backend tests do not run on pull requests #388

Checklist

• Ran npx prettier --write . (for formatting)
• Ran gofmt -w . (for Go backend)
• Ran npm test (for JS/TS testing)
• Added unit tests, if applicable
• Verified all tests pass
• Updated documentation, if needed

[github-actions]

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