Fix gallery integration card crash from invalid mock hassUrl (#30126)

The gallery mock set hass.auth.data.hassUrl to an empty string, which
caused brandsUrl() to throw when constructing a URL via new URL(base, '').
In production hassUrl is always a valid URL, so the mock now uses
location.origin to match real behavior.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/fake_data/provide_hass.ts

@@ -196,7 +196,7 @@ export const provideHass = (
     // Home Assistant properties
     auth: {
       data: {
-        hassUrl: "",
+        hassUrl: location.origin,
       },
     } as any,
     connection: {