Add Helm chart for developer-portal-controller deployment

## Summary

Add a Helm chart for developer-portal-controller to enable standardized deployment via KuadrantControlPlane.

Currently, developer-portal-controller is deployed via inline code in kuadrant-operator's reconciliation logic. Moving to a Helm chart aligns with how other components (dns-operator, authorino-operator, limitador-operator, mcp-gateway) are deployed.

## Requirements

Create `/charts/developer-portal-controller/` with minimal structure:
```
charts/developer-portal-controller/
├── Chart.yaml
├── values.yaml
└── templates/
├── deployment.yaml
├── serviceaccount.yaml
├── clusterrole.yaml
├── clusterrolebinding.yaml
└── _helpers.tpl
```

The Deployment template should mirror the inline code currently in kuadrant-operator's `internal/controller/developerportal_reconciler.go` (specifically the `buildDeployment()` function).

## Related Issue

https://github.com/Kuadrant/kuadrant-operator/issues/2264