v0.1.9

1. Added an SDM Usage Audit to the beta migration tools.
2. Reports the total number of Simple Download Monitor download records.
3. Shows how many unique SDM downloads are referenced by standard download shortcodes.
4. Detects direct sdm_process_download links.
5. Detects SDM counter, info, link, and hidden-download shortcode references.
6. Reports SDM references found in post meta/page-builder data.
7. Added a No Direct Reference Found category for downloads without an individually detected reference.
8. Detects SDM category/listing shortcodes that may expose downloads dynamically.
9. Added warnings so unreferenced downloads are not incorrectly assumed to be unused.
10. Added a detailed review table for auditing individual SDM download records and their detected usage.
11. Keeps the migration process conservative: the usage audit does not change which items are considered safe for automatic replacement.
12. Preserved existing migration rollback and dry-run behavior.
13. Included minor admin UI styling improvements for migration action icons.
14. Updated README and changelog documentation.