Implement Plex-compatible file-extension coercion to avoid Plex silently ignoring .mp4 (and single-file .m4a) audiobooks (issue #166). Adds a DB migration and configuration key (plex_format_coercion_enabled, default true), exposes a toggle in the setup wizard and Admin Paths settings, and persists/reads the setting in the admin/setup APIs.
Introduces src/lib/utils/format-coercion.ts (coerceToPlexCompatible) and related constants in src/lib/constants/audio-formats.ts (PLEX_COMPATIBLE_EXTENSIONS, COERCION_RENAME_MAP, DRM_EXTENSIONS, TRANSCODE_REQUIRED_EXTENSIONS). The organize-files processor now runs coercion after organizing/tagging and before generating the filesHash and triggering scans; coercion is idempotent, never overwrites existing targets, logs warnings on DRM/transcode/permission errors, and is non-fatal.
Adds unit tests for the coercion util and updates processor & setup UI tests. Updates documentation (TABLEOFCONTENTS, file-organization, fixes/file-hash-matching, settings-pages) describing behavior, config, and constraints.
Introduces 'series' and 'seriesPart' fields to the Audiobook model and database schema. Updates API routes, file organization, and path template utilities to support series metadata. Enhances chapter merging logic, improves notification backend testing, and expands test coverage for admin and API routes.
kikootwo