MVP: Wire API to @worksight/common types

**Parent:** #14

## Bottom line
Nest API endpoints return / accept shapes from `@worksight/common` types; users/tasks (or equivalent) controllers use shared types.

## Done means
- [ ] Shared types imported in API modules
- [ ] At least one list endpoint returns common-shaped fixtures or DB rows mapped to common types
- [ ] Type-check green
