- Add _region_picker.html template with Leaflet map and editable rectangle
- Add Leaflet 1.9.4 and Leaflet.draw 1.0.4 CDN deps to adapters_edit.html
- Update GET /adapters/{name} to fetch map_tile_url from config.system
- Update POST /adapters/{name} to validate and save region coordinates
- Validation: -90 <= south < north <= 90, -180 <= west < east <= 180
- Region changes flow through to audit log via existing settings capture
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
