feat(android): UPnP picker foundation (UPnP slice 3/6)

UpnpRoute - narrow domain model for a discovered UPnP / DLNA
renderer. Carries the AVTransport + RenderingControl control URLs
the SOAP client uses.

CastApi - Retrofit interface for the new POST /api/cast/stream-token
endpoint (UPnP slice 2/6). Returns {token, exp, url} for the
selection path.

OutputRoute.fromUpnpRoute - companion factory that tags the route
with Protocol.UPNP. Subtitle is 'Manufacturer Model' or falls back
to 'Network speaker' when description fields are blank.

CHANGE_WIFI_MULTICAST_STATE manifest permission - install-time on
all API levels, no runtime prompt. Required for SSDP multicast
discovery.

Discovery + SOAP + integration land in follow-up commits.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

android/app/src/main/AndroidManifest.xml

@@ -10,6 +10,7 @@
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
     <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />
     <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
+    <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
 
     <application
         android:name=".MinstrelApplication"