- Add `obsoleted.rs` module to handle storing, metadata management, and operations for obsoleted packages.
- Implement commands for marking, listing, searching, restoring, exporting, and importing obsoleted packages (`pkg6repo`).
- Enhance `RepositoryError` with `From` implementations for various error types to manage database and serialization-related errors.
- Introduce reusable data structures for obsoleted package metadata and export representation.
- Update `Cargo.toml` and `Cargo.lock` to include new dependencies (`redb`, `bincode`, etc.).
- Document obsoleted package workflow and integration details in `doc/obsoleted_packages.md` for contributors.
- Refactor repository internals to integrate obsoleted package support without disrupting existing workflow.
- Add robust error handling, logging, and pagination for enhanced usability and scalability.
- Replace manual recursive directory scanning with `walkdir` for simplified and efficient file traversal.
- Update dependencies in `Cargo.toml` and `Cargo.lock` to include `walkdir`.
- Enhance code maintainability by replacing redundant logic with streamlined traversal and processing.
