Fix authentication failure when opening channel media attachments

## Describe the bug

Media attachments can fail to load after being posted to a Buzz channel. Opening the attachment URL returns the JSON error `{"error":"authentication failed"}` instead of the uploaded image.

## Steps to reproduce

1. Post an image attachment in a Buzz channel.
2. Open the attachment or its media URL.
3. Observe the attachment response.

## Expected behavior

The attachment should render or download for an authorized Buzz user/channel member without an authentication error.

## Actual behavior

The media endpoint responds with `{"error":"authentication failed"}`.

## Version and platform

- Buzz version: unknown
- OS: macOS (exact version unknown)

## Logs / additional context

Observed media URL:
https://yusuf.communities.buzz.xyz/media/7cbcfa927d5c6d428953e915ae7e19687b0c70fa262b9d7465b49f2f74734d46.png

Screenshot:

This may indicate that the attachment renderer or direct media route does not carry the required authenticated session. That is a hypothesis, not a confirmed root cause.

Start by locating the media URL endpoint and its authentication handling, then reproduce the failure with the affected Buzz attachment URL. Trace how an authorized channel member session is checked for media requests; done means authorized users can render or download the attachment without the authentication error.

Written by the indexing model from the issue text.