Co-authored-by: Michael T Chuang <github@michaeltchuang.com>

With secure_delete on, zeroing a freed page first journals the page's
original content. Past 64 KiB SQLite spills that journal to an unlinked
temp file that is never overwritten, so the partkey/registry migrations
and large registry flushes left copies of voting subkeys on disk. Set
PRAGMA temp_store=MEMORY in a ConnectHook: it must be in effect before
BEGIN, so it cannot be set inside the transaction.

feat: identify nodekit via user-agent

fix: re-exec updated NodeKit before upgrading Algorand