feat(argo-rollouts): Add Gateway API HTTPRoute support for the dashboard

[somaz94]

Adds optional Gateway API HTTPRoute support for the Argo Rollouts dashboard, mirroring the existing dashboard.ingress option. Lets users expose the dashboard through a Gateway API gateway instead of an Ingress controller. Disabled by default (dashboard.httproute.enabled: false), so the change is fully backwards compatible. Follows the pattern already merged for the argo-cd and argo-workflows charts.

Validation:

• helm lint charts/argo-rollouts → 0 failed
• helm template with dashboard.httproute.enabled=true renders a valid HTTPRoute (parentRefs / hostnames / backendRefs to the -dashboard service on port 3100)
• Default values render nothing (gated on dashboard.enabled && dashboard.httproute.enabled)
• Empty-matches edge case renders a valid rule (backendRefs-first)
• ./scripts/helm-docs.sh run; README regenerated; chart version 2.40.10 → 2.41.0; artifacthub.io/changes updated

Checklist

• Version bumped (2.40.10 → 2.41.0, MINOR — new optional feature)
• Documentation regenerated via ./scripts/helm-docs.sh
• artifacthub.io/changes annotation updated
• Backwards compatible (disabled by default)
• DCO sign-off present
• One chart per PR (argo-rollouts only)