Deploy backend to AWS

[irithsharma]

Justification

Set up deployment to AWS through pipeline.

Major changes

Minor changes

• Updated pipeline to run only on main branch commits and PRs.
• Renamed PR template to pull_request_template.md as per docs.

Effects

• Pipeline only runs for PRs or main changes.
• PR template is provided on all future pull requests.

---

• [ ] Linked relevant ticket, or provided justification for change
• [ ] Code is commented/documented well to ensure readability.
• [ ] Unit testing:
  • [ ] Implemented/updated.
  • [ ] Run locally without any failures.
  • [ ] Run in PR pipeline without any failures.
• [ ] Integration testing
  • [ ] Implemented/updated.
  • [ ] Run locally without any failures.
  • [ ] Run in PR pipeline without any failures.
• [ ] Linter scan for branch has no new issues and tests introduce > 80% coverage.
• [ ] Release
  • [ ] Author of PR is available during deployment time to monitor release.