Fix development production build and migration startup

[kevinwmerritt]

Summary

• use NodeJS.Timeout for scheduled interval handles so the production TypeScript build accepts clearInterval
• give AddExternalIdToContacts1750299580000 an explicit migration name so TypeORM can identify it after production minification

Why

The packaged development build currently fails in two places:

1. TypeScript rejects NodeJS.Timer when it is passed to clearInterval with the current locked typings.

2. When upgrading an existing server database, the production-minified contact migration has the runtime class name t. TypeORM requires migration names to end in a 13-digit timestamp and aborts startup with:

   t migration name is wrong. Migration class name should have a JavaScript timestamp appended.

The older migrations already define an explicit name property for this reason.

Verification

• ESLint passes for both changed files.
• npm run build --workspace @bluebubbles/server succeeds.
• A packaged ARM64 build starts successfully against an existing BlueBubbles 1.9.9 configuration database on macOS 15.7.7.