fix(cloud): declare dotenv for repository-owned startup scripts

The full CI Smoke lanes job on 58cc489bb65e67db4cdb8cf70b6431d217599d72 cannot start the cloud API: packages/cloud/scripts/admin/local-dev-helpers.ts imports dotenv, but these repository-owned scripts have no package manifest and the root workspace does not declare the dependency. Declaring it only in the sibling cloud API workspace does not make it resolvable from the scripts under an isolated install.

Evidence: https://github.com/elizaOS/eliza/actions/runs/35281353131/job/105404052619 reports ENOENT resolving dotenv during sync-api-dev-vars after database migrations succeed.

Acceptance: declare the dependency at its owning boundary, preserve existing environment-file precedence, verify resolution after a normal frozen install, run the existing local-dev helper consumers, and pass the complete hosted smoke lane.