[Feature Request]: Add visual indicator for collapsed connection group with active connection

### Feature Description

Visual cue to indicate when a collapsed connection group contains an active connection.

### Problem and Motivation

When server or database connections are saved within a connection group and the groups are minimized, I can't tell which groups have active connections within them. Some kind of visual cue, even a simple bold heading at the connection level would be appreciated. Thanks

### Related Area

- [x] Connection dialog
- [ ] Query results panel
- [ ] Query editor
- [ ] Object Explorer
- [ ] Table Designer
- [ ] Schema Compare
- [ ] Schema Designer
- [ ] Local container
- [ ] GitHub Copilot integration
- [ ] Query Plan Visualizer
- [ ] Other (please describe below)

### If you selected "Other", please describe the area

_No response_

### Confirmation

- [x] I have searched existing feature requests and couldn't find a match
- [ ] I want to help implement this feature

Start by locating the TypeScript implementation of the Connection dialog and its collapsed connection-group rendering. Confirm how active connections are represented, then define and implement a visible cue for a collapsed group containing one; the work is done when the cue is clear in the minimized group state.

Written by the indexing model from the issue text.