This commit includes the following changes:
- Refactored all data repositories in `internal/data/sql/` to use a consistent `sql` package and to align with the new `domain` models.
- Fixed the GraphQL structure by moving the server creation logic from `internal/app` to `cmd/api`, which resolved an import cycle.
- Corrected numerous incorrect import paths for packages like `graph`, `linguistics`, `syncjob`, and the legacy `models` package.
- Resolved several package and function redeclaration errors.
- Removed legacy migration code.
