Add undocked window visibility options (tab bar, close button, standalone mode) to RDM Linux

Product: Remote Desktop Manager for Linux
Desktop: Fedora 44, KDE Plasma (Wayland)

Description:
The Windows version of RDM exposes several undocked-window visibility options under File – Settings – User Interface – Tabs that are not present in the Linux build:

- Show tab bar on undocked windows
- Show close button on undocked windows
- Undocked windows: Standalone (no tabs) / other modes
- Lock tabs in place
- Show folder name in tab title
- Use single-line tabs with overflow

Current behavior on Linux:
An undocked session window always renders with RDM's tab bar attached. There is no setting to suppress it.

Why it matters:
When working full-screen in a remote session (e.g. Visual Studio over RDP), the persistent tab bar consumes vertical space and adds visual chrome that isn't useful once the session is already in its own window. On high-resolution displays this is a usable-area and focus issue, not just cosmetic.

Expected behavior:
Bring the existing Windows "Undocked windows" visibility settings to the Linux build — at minimum "Show tab bar on undocked windows" and the "Standalone (no tabs)" undocked mode.

Notes:
The settings already exist and are well-defined on Windows, so this is a parity request rather than new design work.