refactor: rename service to autostart, fix fork bomb, add rfd file picker, use dirs crate, auto-start launcher, propagate overlays, ensure icon

- Rename service module to autostart (no systemd service is used)
- Fix fork bomb: replace subprocess spawning with thread::spawn
- Replace zenity/kdialog with rfd crate for XDG Portal file picker
- Use dirs crate instead of env::var("HOME")
- Auto-start launcher before game launch for online auth
- Propagate gamemode/mangohud env vars to launcher process
- Auto-install SVG icon on startup via ensure_icon()
- Add assets/umutray.svg
- Remove stale zenity/kdialog optdepends from PKGBUILD
- Update .gitignore for .claude/ and CLAUDE.md

umutray.desktop

@@ -2,7 +2,7 @@
 Name=umutray
 Comment=Wine launcher manager for Windows game launchers
 Exec=umutray gui
-Icon=applications-games
+Icon=umutray
 Type=Application
 Categories=Game;
 Keywords=wine;proton;gaming;launcher;