Update backend dependencies via npm update (#227)

Routine minor/patch dependency update for the backend, containing only
the effects of `npm update` (no code changes).

- @aws-sdk/* packages bumped to latest minor/patch (client-ses,
  client-ssm 3.1086.0 -> 3.1088.0, and related core/credential-provider/
  nested-clients/token-providers/types/xml-builder/signature-v4)
- @smithy/* transitive packages bumped to latest patch

Only backend/package-lock.json is modified; package.json ranges unchanged.


Claude-Session: https://claude.ai/code/session_01KQrCZNBP4x3KrDyqHC5QSg

Co-authored-by: Claude <noreply@anthropic.com>

Author: smessmer