The users, download history and activity view-state databases open their
connections with SQLite's default busy timeout of 5 seconds. A start-up
migration, the restart reconcile, or any statement that overlaps a
backup or a second process raised "database is locked" after 5 seconds,
and the reconcile finished only part of its work.
One shared `DB_BUSY_TIMEOUT_SECONDS` (30) in `core/utils.py`, used by
all three. The test reads SQLite's `busy_timeout` pragma back from each
connection, so it doesn't need a real lock fight.
I left `UserDB.initialize()` without a guard on purpose. With 30 seconds
the wait covers a backup, and swallowing a schema failure there would
hide a worker that can't run.
Found in a Claude pass over 1.5.0.
