Bump rust from 1.86 to 1.87 in /backend
Bumps rust from 1.86 to 1.87.
---
updated-dependencies:
- dependency-name: rust
dependency-version: '1.87'
dependency-type: direct:production
update-type: version-update:semver-minor
...
Signed-off-by: dependabot[bot] <support@github.com>