ShellHub: Cross-tenant IDOR in `GET /api/namespaces/:tenant` via API Key bypasses membership check

ShellHub is a centralized SSH gateway. Prior to 0.24.2, GET /api/namespaces/:tenant returns the full namespace object — including the members list (user IDs, e-mails, roles), settings, and device counts — to any caller authenticated by an API Key, for any tenant, regardless of the API Key's own tenant scope. The handler conditionally skips the membership check when the user ID (X-ID) is absent, which is exactly the case for API Key authentication. This vulnerability is fixed in 0.24.2.