nebula-mesh: Web UI lacks CSRF tokens on /ui/* mutating endpoints

nebula-mesh is a self-hosted control plane for Slack Nebula mesh virtual private network. Prior to version 0.3.3, every /ui/* POST / PUT / PATCH / DELETE route processes the request as soon as the session cookie validates. SameSite=Lax on the session cookie prevents most cross-site form submits but does not protect: top-level form-submit navigations from third-party pages (some browsers still send Lax cookies on top-level POSTs); same-registrable-domain attackers (sibling-subdomain XSS, subdomain takeover); the GET /ui/logout route, which a third-party <img src=".../ui/logout"> can force-trigger. This issue has been patched in version 0.3.3.