Keep message preview font secondary (dark mode)

### Your use case

#### What would you like to do?
Keep the message preview colour secondary to the room name.

- **For active room:** Room name - bold white; message preview - light-grey.

- **For read room:** Room name - white; message preview - grey.
- _Select/hover should not affect font._
#### Why would you like to do it?
- Make room names easier to identify when scanning the list.
- Giving both the room name and preview the same brightness/colour weakens hierarchy.
#### How would you like to achieve it?
- Use a lower-contrast text colour (grey) for message previews while keeping a brighter colour (white/bold) for room names.
- Apply the same hierarchy for read, hovered, selected, and active room states.

### Have you considered any alternatives?

> - **For active room:. . .message preview - light-grey
>- _Select/hover does not affect font._

1. Hovering/selecting a room (not just activity), makes the message preview light-grey .
However it will not make the title bold.

> - **For read room:** Room name - white; message preview - grey.

2. **For read room:** Room name - light-grey; message preview - grey.
Hovering/selecting room makes the title white and the message preview light-grey.

### Additional context

_No response_

Start by locating the room-list message preview component and its dark-mode styling, then inspect how active, read, hover, and selected states set text appearance. Done means room names remain visually stronger than previews in each listed state, with preview contrast reduced and hover or selection not changing the font hierarchy.

Written by the indexing model from the issue text.