fix(k8s): add alpha prefix in production

Author: douglasduteil

.k8s/environments/prod/app.ts

@@ -0,0 +1,5 @@
+import { GlobalEnvironment } from "@socialgouv/kosko-charts/types";
+
+export default {
+  subdomain: `alpha-${process.env.CI_PROJECT_NAME as string}`,
+} as Partial<GlobalEnvironment>;