The pending_devices.properties column is added by an idempotent migration, so
existing rows have properties = NULL. PendingDeviceResponse typed it as a list,
so GET /scan/pending 500'd on any pre-existing device.
- Coerce NULL/non-list properties to [] in PendingDeviceResponse.
- Backfill existing NULL rows to '[]' in init_db migrations.
- Regression test: /scan/pending returns 200 with a legacy NULL-properties row.
ha-relevant: maybe
Pouzor
abefc42fdf