security(deps): update dompurify to 3.3.3 (#31)

## Summary
- Updates `dompurify` from `3.3.1` to `3.3.3` in lockfile
- Fixes
[GHSA-v2wj-7wpq-c8vv](GHSA-v2wj-7wpq-c8vv)
(moderate severity)
- Unblocks Dependabot PRs #25, #28, #29, #30 whose security checks fail
due to this vulnerability

## Test plan
- [ ] CI passes (quality, security, build, mutation, sbom)
- [ ] `pnpm audit --prod --audit-level=moderate` reports no
vulnerabilities

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: marcstraube