- Introduce `CustomStringRule` and `CustomFileRule` for user-defined patterns
- Add `RedactionPolicy` to encapsulate rules and custom detection config
- Support `--custom-string`, `--custom-file`, and `--source-path` CLI flags
- Propagate source path through detection and redaction for file-level context
- Update HTTP API to accept `RedactionPolicy` and optional `source_path`
- Bump version to 0.2.9 and update dependencies

Signed-off-by: Cloudiful <bunnies-spender.0h@icloud.com>