SchedulerConfig.__init__ maps legacy auto_download/folder_scan keys to the
primary auto_download_after_rescan/folder_scan_enabled fields. However,
model_dump() was including auto_download=null and folder_scan=null in
serialised output. When this was written to config.json and reloaded,
those keys were present (albeit null), so the alias mapping was skipped
and the primary fields retained default False values instead of the
configured True values.
Fix:
- Override SchedulerConfig.model_dump() to drop None-valued alias fields
before returning the serialised dict.
- ConfigService.save_config() re-serialises the scheduler field through
its overridden model_dump() so the fix applies when writing to disk.
Tests added:
- test_roundtrip_excludes_none_alias_fields: verifies model_dump omits
null auto_download/folder_scan keys.
- test_save_and_load_scheduler_flags_roundtrip: end-to-end roundtrip
through ConfigService confirms raw JSON and loaded values match.
Pre-existing failure in test_core_error_handler.py is unrelated.
