Use dash_app.get_asset_url() to ensure image paths respect the
X-Ingress-Path header (requests_pathname_prefix).
- Update all SVG image paths in control.py, figures.py, and views.py
to use get_asset_url() instead of hardcoded 'assets/images/...' paths
- Add test_svg_images_with_ingress_path() to verify image paths
contain the correct prefix when X-Ingress-Path header is present
Fixes issue where image paths were not prefixed in Home Assistant
ingress proxy setups.