The ncruces/go-sqlite3 driver does not always auto-convert TEXT columns
to time.Time. This caused scan errors on updated_at/created_at fields,
blocking witness startup.
Fix: Scan timestamps into sql.NullString and parse with parseTimeString()
helper that handles RFC3339Nano, RFC3339, and SQLite native formats.
Fixes: bd-4dqmy
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>