Requirements from App Service website resources bleed into unrelated compute resources

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When an application defines multiple compute environments (e.g., one for Azure Container Apps and one for App Service), requirements from the App Service website flow into all compute resources, even those not associated with the App Service environment.

Reproduction steps

1. Create an app with two compute resources.
2. Create two compute environments: one ACA compute environment and one App Service compute environment.
3. Associate one of the compute resources with ACA and the other with AppService using WithComputeEnvironment(...).
4. Deploy or publish the app.

Actual behavior

A compute resource that is not associated with the App Service environment still triggers App Service validation errors. For example, you see errors such as:

The endpoint 'http' on resource 'pythonapp-standalone' is not external. App Service only supports external endpoints.

even though the resource is mapped to ACA, not App Service.

The app model creates deployment targets for all compute environments up front. Validation happens against all of them, and only later do we select the compute environment associated with each resource. That ordering causes requirements from the App Service environment to leak into unrelated resources.