Helm manifests not generating initContainers correctly in Kubernetes

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

When using Aspire to configure initContainers in Kubernetes deployments, the generated Helm manifests do not include the initContainers properly. This prevents critical initialization tasks (such as database migrations) from running before the main container starts.

### Describe the solution you'd like

Helm manifest generation should correctly include initContainers definitions so that they are applied in Kubernetes clusters. This would ensure that initialization logic runs as expected before the main service container becomes ready.

### Additional context

- Related to the work started in issue #921 regarding startup order and readiness checks.
- The current implementation works in non-Kubernetes scenarios, but Helm manifests are missing the initContainers.
- This impacts scenarios like EF Core migrations, where the init container must run before the application container

Start at the Helm manifest generation path and compare its Kubernetes output with the non-Kubernetes behavior described in the issue. Verify generated manifests include the configured initContainers and preserve their required startup ordering, including the EF Core migration scenario.

Written by the indexing model from the issue text.