Group photos when multiple photos are sent

### Your use case

#### What would you like to do?

On a family group chat when sending pictures, the history of the chat gets flooded by photos when some one sends a number of photos at a time. Other chat applications similar to Element handle this by grouping the photos, presenting miniatures for second, third photos and a "+ number of photos" for the rest. That way the user can open a sort of gallery and scroll through the photos.

#### Why would you like to do it?

This enables people to share more on Element, instead of having to limit their use.

#### How would you like to achieve it?

I don't know if this requires a different type of message in Element of if it can be made through grouping sequential attachments.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_

### Are you willing to provide a PR?

No

The issue names no files, tests, or entry points. Start by determining whether sequential attachments can be grouped in the Android app's Jetpack Compose UI or require a Matrix Rust SDK message-model change. Done means multiple photos appear as a compact gallery with previews and a remaining-photo count.

Written by the indexing model from the issue text.