Message Previews: Drafts

### Your use case

#### What would you like to do?
1. Pin Rooms with drafts to the top of the Room list.
2. Indicate draft message with pencil icon in message preview.
#### Why would you like to do it?
Pinning rooms with drafts makes them easier to find and reduces the chance of forgotten messages.

### Have you considered any alternatives?

Add transient 'Drafts' filter.

### Additional context

_No response_

### Are you willing to provide a PR?

No

No files or tests are named. Start by tracing the Android room-list entry point and the message-preview rendering path, then inspect how draft state is represented; done means rooms with drafts are prioritized and draft previews show a pencil icon, with the relevant tests updated or added.

Written by the indexing model from the issue text.