This commit isolates the `Work` aggregate into its own package at `internal/domain/work`, following the first step of the refactoring plan in `refactor.md`.
- The `Work` struct, related types, and the `WorkRepository` interface have been moved to the new package.
- A circular dependency between `domain` and `work` was resolved by moving the `AnalyticsRepository` to the `app` layer.
- All references to the moved types have been updated across the entire codebase to fix compilation errors.
- Test files, including mocks and integration tests, have been updated to reflect the new structure.
