fix: biometric auth, workflow error propagation, execution logs

- Biometric: persist preference to SecureStore so it survives restarts;
  actually call LocalAuthentication.authenticateAsync() at startup and
  block navigation behind a locked screen until the user authenticates
- Workflow run: remove silent error swallowing in triggerWorkflow so
  failures surface as toasts; success snackbar only shown on API success
- Execution logs: add includeData=true to fetchExecutionById so n8n
  returns node-level data and error messages instead of an empty object

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/screens/SettingsScreen.tsx

@@ -122,6 +122,7 @@ const SettingsScreen: React.FC = () => {
               SecureStore.deleteItemAsync(SECURE_STORE_KEYS.BASE_URL),
               SecureStore.deleteItemAsync(SECURE_STORE_KEYS.API_KEY),
               SecureStore.deleteItemAsync(SECURE_STORE_KEYS.APP_TOKEN),
+              SecureStore.deleteItemAsync(SECURE_STORE_KEYS.BIOMETRIC_ENABLED),
             ]);
             setBaseUrl('');
             setApiKey('');