feat: call ui scaffold

src/lib/stores/index.ts

@@ -50,6 +50,7 @@ export const showSidebar = writable(false);
 export const showSettings = writable(false);
 export const showArchivedChats = writable(false);
 export const showChangelog = writable(false);
+export const showCallOverlay = writable(false);
 
 export type Model = OpenAIModel | OllamaModel;