feat(web): make google cast opt in (#18514)

* add setting switch

this isnt bound to anything yet

* make google casting opt-in

* doc updates

* lint docs

* remove unneeded translation items

* update mobile openai defs

* fix failing test

we need to mock user prefs since CastButton uses it

server/src/types.ts

@@ -502,6 +502,9 @@ export interface UserPreferences {
     showSupportBadge: boolean;
     hideBuyButtonUntil: string;
   };
+  cast: {
+    gCastEnabled: boolean;
+  };
 }
 
 export interface UserMetadata extends Record<UserMetadataKey, Record<string, any>> {