* fix sub label filter for non-ascii names
The sub_labels filter lowercased the requested name in Python but the stored value with SQLite's LOWER(), which only folds ASCII. Cyrillic and other non-ASCII names never matched, so filtering by a face name returned no events. Both sides are now lowered in SQLite, which keeps ASCII matching case-insensitive and non-ASCII matching exact.
* cover events/search in sub label filter test