Host setup improvements

[khvn26]

1. Introduce top-level apiHost, frontendHost keys.
2. Populate ingress.api.hosts and ingress.frontend.hosts values from the above, unless overridden. Add /version and /sales-dashboard to default path list for the backend.
3. Ideally, populate the default Django sites object with the frontend hostname. Alternatively, set api.env.FLAGSMITH_DOMAIN to frontendHost value.
4. When separateApiAndFrontend is set to true, set frontend.frontend.apiProxy.enabled to false and frontend.env.FLAGSMITH_API_URL to apiHost.