Add zod payload contracts for admin API routes (#358)

* Add zod route payload contracts for admin APIs

* Fix review follow-ups for zod admin payloads

* Refactor account payload parser helpers

src/server/services/siteProxy.ts

@@ -95,7 +95,7 @@ type UndiciConnectOptions = {
   httpSocket?: Socket;
 };
 
-function normalizeSiteUrl(value: string): string {
+export function normalizeSiteUrl(value: string): string {
   const trimmed = (value || '').trim();
   if (!trimmed) return '';