fix: remove remaining Sora references from frontend

The previous Sora removal missed several frontend references, causing
TypeScript build errors for sora_client_enabled and a missing SoraView.vue
import. Clean up all remaining Sora code from types, router, sidebar,
settings, store, and accounts API.

frontend/src/stores/app.ts

@@ -332,7 +332,6 @@ export const useAppStore = defineStore('app', () => {
         custom_menu_items: [],
         custom_endpoints: [],
         linuxdo_oauth_enabled: false,
-        sora_client_enabled: false,
         backend_mode_enabled: false,
         version: siteVersion.value
       }