When a user renames a series via the UI, the scanner was using the
filesystem directory name to overwrite the DB series name, effectively
undoing the rename. This adds an original_name column to series_metadata
that tracks the filesystem-derived name, so the scanner can map it back
to the user-chosen name. The migration also back-fills existing renamed
series by comparing book file paths with DB series names.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
