refactor: creation button disaster recovery

src-tauri/src/settings_manager.rs

@@ -991,6 +991,17 @@ pub async fn save_sync_settings(
   sync_server_url: Option<String>,
   sync_token: Option<String>,
 ) -> Result<SyncSettings, String> {
+  // Cloud login and self-hosted sync share the same sync engine and a
+  // profile can't be sync'd to two backends at once. Block any *write*
+  // (non-null URL or token) while the user is signed into their cloud
+  // account — the clearing path (both `None`) is always allowed so logged-
+  // in users can wipe a stale self-hosted config that pre-dates their
+  // sign-in.
+  let is_setting_self_hosted = sync_server_url.is_some() || sync_token.is_some();
+  if is_setting_self_hosted && crate::cloud_auth::CLOUD_AUTH.is_logged_in().await {
+    return Err(serde_json::json!({ "code": "SELF_HOSTED_REQUIRES_LOGOUT" }).to_string());
+  }
+
   let manager = SettingsManager::instance();
 
   manager