Ignore the parallel test databases

The existing pattern only matched db/test.sqlite3, so the per-worker
databases rake test writes alongside it (db/test.sqlite3_0 and friends)
showed up as untracked.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: hsbt

.gitignore

@@ -1,5 +1,5 @@
 .bundle
-db/*.sqlite3
+db/*.sqlite3*
 log/*.log
 tmp/
 .DS_Store