[Linux] --start-minimized still shows "unknown" window in GNOME app switcher

Description

When running LibrePods with --start-minimized on GNOME (Wayland), the app correctly starts with only the tray icon visible. However, an "unknown" window still appears in the GNOME app switcher (Alt+Tab).

Environment

• OS: Fedora 44
• DE: GNOME (Wayland)
• GPU: NVIDIA RTX 5070 (proprietary driver 595.80)
• LibrePods version: v0.1.0 AppImage (linux-v0.1.0 release)
• Launch command: WGPU_BACKEND=gl librepods-x86_64.AppImage --start-minimized
• Note: WGPU_BACKEND=gl is required because Vulkan crashes with ERROR_SURFACE_LOST_KHR on this setup

Expected Behavior

When started with --start-minimized, the app should only show the system tray icon with no window in the app switcher.

Actual Behavior

A window labeled "unknown" appears in the GNOME app switcher. The tray icon works correctly.

Possible Cause

The GPU rendering surface (wgpu/EGL window) is likely being created even in minimized mode. On GNOME Wayland, any mapped surface — even hidden — appears in the app switcher unless the appropriate window type hints are set or the surface is not created at all.

Suggested Fix

In --start-minimized mode, either:

1. Don't create the GPU surface until the user explicitly opens the window from the tray
2. Set the window role/type so GNOME excludes it from the switcher
3. Unmap/destroy the surface after initialization if running headless

No source files or tests are named. Start at the --start-minimized handling and window/GPU surface initialization, then reproduce with the provided AppImage command on GNOME Wayland. Done means minimized startup shows only the tray icon and no "unknown" entry in the app switcher.