feat: Add proxying support for images (#2427)

- Closes #2418

docs/configuration/common/proxy-warning.md

@@ -0,0 +1,23 @@
+There are [security and performance
+implications](https://github.com/dermotduffy/hass-web-proxy-integration?tab=readme-ov-file#considerations)
+to consider before installing
+[hass-web-proxy-integration](https://github.com/dermotduffy/hass-web-proxy-integration)
+and using this functionality.
+
+If the
+[hass-web-proxy-integration](https://github.com/dermotduffy/hass-web-proxy-integration)
+is not detected, the card will fall back to the original URL unless proxying was
+explicitly enabled (i.e. set to `true`), in which case an error will be shown.
+
+> [!WARNING]
+> When proxying, the card's ability to ensure caching doesn't interfere with
+> refresh accuracy depends on what is being proxied. Specifically, `image`
+> based proxying will have less reliable behavior because signed URLs cannot
+> have additional query parameters added without invalidating the signature. The
+> card uses a URL fragment (`#_t=...`) for cache-busting instead, which does not
+> affect the signature but is less reliable: the fragment is not sent to the
+> server, so the browser may serve a cached response. Reliable refreshing will
+> depend on the source server providing appropriate `Cache-Control` headers. The
+> Home Assistant companion app's WebView does not re-fetch images when only the
+> fragment changes, so proxied image refreshing will not work in the companion
+> app.