Scaffold Astro/Strapi monorepo for the site rebuild

Set up a pnpm workspace with apps/site (Astro) and apps/cms (Strapi,
SQLite-backed) as the foundation for the new digital-legacy site.
Switches package management to pnpm and adds Biome for linting/
formatting, replacing npm/no-linter setup. Existing Zola site stays
in place for now and will be migrated/removed progressively.

apps/cms/config/admin.ts

@@ -0,0 +1,25 @@
+import type { Core } from '@strapi/strapi';
+
+const config = ({ env }: Core.Config.Shared.ConfigParams): Core.Config.Admin => ({
+  auth: {
+    secret: env('ADMIN_JWT_SECRET')!,
+  },
+  apiToken: {
+    salt: env('API_TOKEN_SALT')!,
+  },
+  transfer: {
+    token: {
+      salt: env('TRANSFER_TOKEN_SALT')!,
+    },
+  },
+  secrets: {
+    encryptionKey: env('ENCRYPTION_KEY')!,
+  },
+  flags: {
+    nps: env.bool('FLAG_NPS', true),
+    promoteEE: env.bool('FLAG_PROMOTE_EE', true),
+    docLinks: env.bool('FLAG_DOC_LINKS', true),
+  },
+});
+
+export default config;