Add /visitors/ blueprint with REST API endpoints for listing profiles and
visits, labeling (with consent gate), household linking, ignore/unignore,
and cascading forget. Register blueprint in app.py. Add dashboard and profile
detail templates (Bootstrap 5 dark, tab navigation, fetch-based JS). All six
API tests pass (339 total).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
