Add next available appointment option on the datetime step.

[veenupunyani]

Summary

1. Adds a Select next available appointment shortcut on the datetime step that fills in the earliest loaded date/time for the selected service and location.
2. Preselects the next available calendar day so the time dropdown is ready without an extra date click.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud