Security audit alerts for vulnerable dependency versions

### Description
A security audit of the repository's dependency tree has revealed known vulnerabilities in some packages.

### Affected Packages & Paths
* **ajv** (via `ajv-formats` / `@daisy/ace-config`)
* **multer** / **busboy** (via `@daisy/ace-http`)

Start by reproducing the repository's dependency audit and tracing the reported paths through ajv, ajv-formats, @daisy/ace-config, multer, busboy, and @daisy/ace-http. Review the dependency manifests and lockfile to identify compatible updates; done means the audit no longer reports these vulnerabilities and the affected dependency chains remain functional.

Written by the indexing model from the issue text.