Release b231

fix: use ctime instead of mtime for database rotation

The previous implementation used metadata.modified() (mtime) to detect when
database rotation was needed. However, SQLite continuously updates mtime during
normal operation (WAL writes, checkpoints, etc.), causing the rotation logic
to never trigger.

Switch to metadata.created() which returns ctime on Unix systems - this only
changes when file attributes change, not when content is written, making it
reliable for monthly rotation detection.