feat: add invite code validity controls

- Add invite code starts/expires fields across contracts, API, Spacetime bindings, and admin UI
- Enforce pending/expired invite code redemption behavior and expose admin status
- Add admin write-operation confirmation guard and documentation
- Add invite code contract/runtime tests

apps/admin-web/src/api/adminApiTypes.ts

@@ -122,6 +122,8 @@ export interface AdminUpsertProfileRedeemCodeRequest {
 export interface AdminUpsertProfileInviteCodeRequest {
   inviteCode: string;
   metadata?: Record<string, unknown>;
+  startsAt?: string | null;
+  expiresAt?: string | null;
 }
 
 export interface AdminDisableProfileRedeemCodeRequest {
@@ -166,6 +168,9 @@ export interface ProfileInviteCodeAdminResponse {
   userId: string;
   inviteCode: string;
   metadata: Record<string, unknown>;
+  startsAt?: string | null;
+  expiresAt?: string | null;
+  status: 'pending' | 'active' | 'expired';
   createdAt: string;
   updatedAt: string;
 }