feat: remove Windows tray icon functionality

[hashbk]

Summary

Remove all tray icon related code, dependencies, and MSI installer configuration for the Windows client. The tray icon is no longer needed on Windows.

Changes

Rust code

• Cargo.toml: Exclude tray-icon, tao, image dependencies from Windows build target
• src/lib.rs: Gate tray module with cfg(not(target_os = "windows"))
• src/tray.rs: Remove Windows-specific code (IPC session count query, click handler, start_query_session_count function, Windows icon path)
• src/core_main.rs: Remove --tray argument handling on Windows; remove auto-start tray logic on Windows
• src/server/connection.rs: Remove tray process spawn on Windows
• src/platform/windows.rs: Remove get_tray_shortcut(), tray_shortcuts variable, tray process tracking in update_me(), tray startup in run_after_run_cmds() and install_service()

MSI installer

• RustDesk.wxs: Remove LaunchAppTray custom action, TryDeleteStartupShortcut action, App.StartupFolder.ShortcutTray component
• AddRemoveProperties.wxs: Remove LAUNCH_TRAY_APP property
• CustomActions.wxs: Remove TryDeleteStartupShortcut action declaration
• CustomActions.cpp: Remove TryDeleteStartupShortcut function implementation
• CustomActions.def: Remove TryDeleteStartupShortcut export
• ShortcutProperties.wxs: Remove STARTUPSHORTCUTS property
• Package.en-us.wxl: Remove SC_Client_Tray and SC_Client_Tray_Desc strings

Cleanup

• Uninstall scripts still remove stale Tray.lnk files for backward compatibility
• Linux and macOS tray functionality remains unchanged

Test plan

• Build and run on Windows to verify no tray icon appears
• Verify service install/uninstall works without tray
• Verify MSI installer works without tray shortcuts
• Verify Linux/macOS tray still works