Set HeatStack status condition for OpenStack authentication failure

This MR improves the user experience during HeatStack reconciliation by explicitly detecting OpenStack authentication failures (e.g. invalid or outdated passwords in secrets.yaml) and updating the HeatStack status with a meaningful condition.

Previously, if authentication failed, the controller would return an error without updating the status. This led to Flux Kustomization timing out and reporting generic messages

Now explicit error message is visible in sylvactl timeout summary

Kustomization/sylva-system/capo-cluster-resources          InProgress                       Kustomization generation is 11, but latest observed generation is 8
╰┄╴HeatStack/sylva-system/heatstack-capo-cluster-resources InProgress                       HeatStack generation is 11, but latest observed generation is 8
   ╰┄╴┬┄┄[Conditions]
      ├┄╴Ready                                             False      AuthenticationFailure Failed to authenticate with OpenStack — please verify credentials, endpoint or secret access
      ╰┄╴Stalled                                           True       AuthenticationFailure Failed to authenticate with OpenStack — please verify credentials, endpoint or secret access

relates to sylva-projects/sylva-core#2657 (closed)