fix(deps): upgrade backstage packages to fix CVE-2026-24046

Upgrades @backstage/backend-defaults (0.13.1 -> 0.13.2) and
@backstage/plugin-scaffolder-node (0.12.1 -> 0.12.3) to address
symlink path traversal in Scaffolder actions (GHSA-rq6q-wr2q-7pgp).

Also removes the redundant patch for @backstage/plugin-scaffolder-backend
3.0.2, which is already the official fix version.

Replaces the previous yarn patch-based mitigation with the official
fix versions. Lockfile changes were applied using yarn-lockfile-surgeon
to minimize transitive dependency impact.

Author: jonkoops