* exponentially slow upload handshakes caused by lack of rd+fn
sqlite index; became apparent after a volume hit 200k files
* listing big folders 5% faster due to `_quotep3b`
* optimize `unquote`, 20% faster but only used rarely
* reindex on startup 150x faster in some rare cases
(same filename in MANY folders)
the database is now around 10% larger (likely worst-case)
