Handle aiohttp.ClientConnectorError by re-raising for storage proxy disconnection

## Context

The current implementation does not handle aiohttp.ClientConnectorError effectively, which can lead to unhandled exceptions related to connection errors in backendai.

## Acceptance criteria

- Re-raise aiohttp.ClientConnectorError in the code where it is caught.
- Ensure that the re-raised error is appropriately handled by backendai to provide meaningful error messages.
- Test the changes to verify that connection-related errors are correctly reported.

## Other information

The suggestion was made to re-raise aiohttp.ClientConnectorError to allow backendai to create new error messages related to connection issues.

[View original message posted by HyeokJin Kim on 10/21/2025, 2:18:28 PM](https://teams.microsoft.com/l/message/19:ecb31b90c31f4cae95f4fcaf29714692@thread.tacv2/1761023908496?parentMessageId=1760917702989)

JIRA Issue: BA-2746