feat: add UI layer (theme, components, screens, main window)
- theme: MinecraftTheme — dark palette with green accents
- components: ServerCard, ProgressBar, PlayButton, SettingsButton, LogoutButton, AvatarImage
- screens: MainScreen (BorderLayout: sidebar + center + bottom bar), LoginScreen (modal form), SettingsScreen (RAM slider + JVM args)
- ui.Launch: wires theme, session, settings into Fyne app
- main.go: delegates to ui.Launch, loads config
- fix: nil-session guard in MainScreen username display
Co-Authored-By: OWL <noreply@anthropic.com>
Vladimir Zagainov
1487360215