Explicitly read the AUTH_SECRET in auto.config.ts, rather than rely o…

…n the framework to read.

packages/server/auth.config.ts

@@ -1,6 +1,7 @@
 import { defineConfig } from 'auth-astro';
 
 export default defineConfig({
+  secret: (import.meta as any).env.AUTH_SECRET,
   providers: [
     /**
      * https://dashboard.int.identitysandbox.gov/service_providers/5237