HTTPRoute backendRef should explicitly render `group`, `kind`, and `weight`

[NPastorale]

Is your feature request related to a problem? Please describe.
Hello there!

When using this chart with HTTPRoute support through ArgoCD, I can see an OutOfSync diff on the generated route even though the resource is healthy and functions correctly.

The diff comes from the backendRef for the Vault Service being rendered differently between the live object and the chart output.

Live manifest

backendRefs:
  - group: ""
    kind: Service
    name: vault
    port: 8200
    weight: 1

Rendered manifest

backendRefs:
  - name: vault
    port: 8200

From a Gateway API perspective, this is still functionally valid. However, the difference still creates unnecessary manifest drift in GitOps workflows and causes the resource to remain OutOfSync.

Describe the solution you'd like
The chart should render the HTTPRoute backend reference explicitly as:

backendRefs:
- group: ""
  kind: Service
  name: vault
  port: 8200
  weight: 1

This would make the rendered manifest deterministic and should avoid this class of drift for GitOps setups.

Describe alternatives you've considered
Making Argo ignore those differences would still work, but it is far less desirable than just having the manifest be rendered with these additional lines.

Additional context
I'm happy to submit a PR with this change if you consider this a reasonable addition.