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

server-rs/crates/spacetime-client/src/mapper.rs

@@ -281,6 +281,8 @@ impl From<module_runtime::RuntimeProfileInviteCodeAdminUpsertInput>
             admin_user_id: input.admin_user_id,
             invite_code: input.invite_code,
             metadata_json: input.metadata_json,
+            starts_at_micros: input.starts_at_micros,
+            expires_at_micros: input.expires_at_micros,
             updated_at_micros: input.updated_at_micros,
         }
     }
@@ -1997,6 +1999,8 @@ pub(crate) fn map_runtime_profile_invite_code_snapshot(
         user_id: snapshot.user_id,
         invite_code: snapshot.invite_code,
         metadata_json: snapshot.metadata_json,
+        starts_at_micros: snapshot.starts_at_micros,
+        expires_at_micros: snapshot.expires_at_micros,
         created_at_micros: snapshot.created_at_micros,
         updated_at_micros: snapshot.updated_at_micros,
     }