- Add methods to find and clean up obsoleted packages older than a specified TTL (`find_obsoleted_packages_older_than_ttl` and `cleanup_obsoleted_packages_older_than_ttl`) in `libips`.
- Implement a new `CleanupObsoleted` command in `pkg6repo` to handle cleanup operations.
- Update workspace `Cargo.toml` files with unified attributes for better consistency.
- Adjust dependencies (`libips` version patterns, `thiserror` updates) and enhance metadata management for obsoleted packages.
- Enhance repository operations by adding batch processing and robust logging during cleanup.
- Standardize formatting by aligning and cleaning up indentation, spacing, and line breaks across multiple modules.
- Enhance logging with improved message formatting for better context and readability.
- Simplify error handling in `pkg6dev`, `pkg6repo`, and core libraries by consolidating redundant patterns and improving clarity.
- Update test cases to reflect formatting and logging changes while extending coverage of edge cases.
- Perform general cleanup, including removing unused imports, refining comments, and ensuring consistent style.
- Modify `rebuild` and `refresh` methods to take `&self` instead of `&mut self`.
- Replace mutable repository instances in `pkg6dev`, `pkg6repo`, and core library with immutable ones.
- Introduce `debug` logging for enhanced traceability during metadata rebuild and refresh.
- Extract and simplify catalog rebuild logic into a dedicated `rebuild_catalog` method.
- General cleanup: remove redundant methods, reorganize logic, and refine comments across affected files.
- Update `FileBackend` to store files in a multi-level directory structure (`xx/yy/hash`) based on hash prefixes.
- Adjust method signatures and logic across `FileBackend`, `pkg6dev`, and `pkg6repo` to support mutable repository operations.
- Add test cases and scripts (`test_file_structure.rs`, `test_repo_operations.sh`) to validate the new file structure.
- Refactor catalog manager to use `RefCell` for interior mutability to enable lazy initialization.
- Clean up redundant and dead code, enhance comments, and replace outdated logic for file handling and metadata operations.
- Centralize package metadata in workspace for consistency.
- Upgrade `pkg6dev` and `pkg6repo` to version `0.5.1`, aligning with new workspace configuration.
- Introduce `EnvFilter` for dynamic logging configuration, defaulting to debug level.
- Add `LoggingEnvError` variant to `Pkg6DevError` with structured diagnostics for improved error handling.
