CVE-2026-46552: NocoDB: Shared-base link access can invite arbitrary users as persistent base members

Shared-base sessions were granted the same base-member capabilities as authenticated viewers. Using only the shared-base UUID (xc-shared-base-id), an attacker could enumerate base members and invite an arbitrary email into the base as a real member. The invited user could then redeem the invite via the normal signup flow and retain authenticated access even after the owner revoked the shared link.