Update dev container configs to use aspire certs instead of dotnet dev-certs

## Summary

The dev container configurations in `get-started/dev-containers.mdx` use `dotnet dev-certs https --trust` in `postStartCommand`/`postCreateCommand`. These should be updated to use `aspire certs trust` instead.

## Locations

- `src/frontend/src/content/docs/get-started/dev-containers.mdx` — 6 instances across multiple devcontainer.json examples

## Notes

- The Aspire CLI needs to be available in the dev container image for this to work
- May require updating the dev container feature/image to include the Aspire CLI
- `aspire-sdk-templates.mdx` also has one instance that should be updated at the same time