Draft: feat(api/v3): WebSocket server implementation [AC-3171]

Closes AC-3171. Implements the WebSocket server.

Review Checklist

If any item is not complete, the merge request is not ready to be reviewed and must be marked Draft:.

• The merge request title is in the format <change type>(<change scope>): <short description> [<task id>]
  • For example, feat(cli): add QR code generation [AC-123]
  • For details, see CONTRIBUTING.md
• The description includes Closes <jira task ID> (or rarely Updates <jira task ID>)
• The change is fully validated by tests that are run during CI
  • In most cases this means a test in "validate.sh"
  • In some cases, a Go test may be acceptable
  • Validation is not applicable to things like documentation updates
  • Purely UI/UX changes can be manually validated, such as changes to human-readable output
  • For all other changes, automated validation tests are an absolute requirement unless a maintainer specifically explains why they are not in a comment on this merge request
• The change is marked with one of the validation labels
  • validationci/cd for changes validated by CI tests
  • validationmanual for changes validated by hand
  • validationdeferred for changes validated by a follow up merge request
  • validationnot applicable for changes where validation is not applicable

Merge Checklist

• CI is passing
• Merge conflicts are resolved
• All discussions are resolved

Related to AC-3171