fix: cell-network name, install error surfacing, health history cleanup

- docker-compose.services.yml: change external network name from
  pic_cell-network to cell-network so store-service compose files can find
  it.  The project-prefixed name was overriding the explicit name: cell-network
  fix in docker-compose.yml when both files were merged by make start.

- service_store.py: normalize docker compose stderr into the error key in
  the 400 response so the Store page shows the actual failure reason instead
  of the generic fallback message.

- app.py: skip health checks for email/calendar/files managers when those
  optional store services are not installed — prevents false Down alerts and
  unnecessary noise in health history.

- Logs.jsx: remove Email/Calendar/Files columns from the health history table;
  they are optional store services, not core builtins that should always appear.

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

api/routes/service_store.py

@@ -62,6 +62,10 @@ def install_service(service_id: str):
         result = _ssm().install(service_id)
         if result.get('ok'):
             return jsonify(result)
+        # Normalize docker compose stderr into the error key so the frontend
+        # can display the actual failure reason rather than a generic message.
+        if not result.get('error') and result.get('stderr'):
+            result = {**result, 'error': result['stderr']}
         return jsonify(result), 400
     except Exception as e:
         logger.error(f'install_service({service_id}): {e}')