Application preferences

[singular0]

There is no settings dialog at all. QSettings holds window geometry, splitter position and the
connection target, and nothing else.

Candidates:

• History retention limit, currently a hardcoded 500 per channel.
• Font scale — the uConsole panel is 1280x480 and the artwork already scales with the system
  font.
• Timestamp format.
• Whether to connect on launch.
• Notification behaviour, once there is any.

Vertical space is the scarce resource, so this belongs in a dialog rather than a pane.