feat: The Steamify shortcut opens the app

Steamify CachyOS on the desktop and in the launcher starts the newest app
(in Konsole the first time, while PySide6 still has to be installed); the
terminal menu is Steamify Terminal in the launcher. A shortcut from before
2.0.1 is ticked in the menu, so a normal run replaces it. steamify-app.sh
leaves the shortcut's launcher entry (same id) alone.

ui/qml/Main.qml

@@ -60,8 +60,9 @@ ApplicationWindow {
         single: { label: "Single user mode", hint: "No password, lock screen or wallet prompts",
                   body: "Like SteamOS: never a login or lock screen, and no KDE wallet password prompts. Typing a password with a controller is no fun.",
                   changes: ["SDDM autologin, no lock screen or user switching", "Valve's empty wallet; your own is kept aside", "Launcher shows Sleep, Restart, Shut Down only"] },
-        launcher: { label: "Steamify shortcut", hint: "Icon on the desktop and in the launcher",
-                    body: "Opens the newest Steamify, so you never need the install command again.", changes: ["Desktop icon and launcher entry"] },
+        launcher: { label: "Steamify shortcut", hint: "The app on the desktop and in the launcher",
+                    body: "Opens the newest Steamify app, so you never need the install command again. Steamify Terminal in the launcher opens the terminal menu.",
+                    changes: ["Steamify CachyOS on the desktop and in the launcher (the app)", "Steamify Terminal in the launcher"] },
         cec: { label: "HDMI-CEC", hint: "Use Steam with the TV remote, TV on/off with the PC", experimental: true,
                body: "Use Steam with your TV remote, and the TV turns on and off with the PC. Turn on CEC on the TV too (Sony: BRAVIA Sync, Samsung: Anynet+, LG: SimpLink).",
                changes: ["Valve's cecd and cec-audio-control", "HDMI CEC section in Steam's Display settings", "Volume buttons for the TV in the Quick Access menu"] },

ui/steamify-app.sh

@@ -53,8 +53,11 @@ if ! python3 -c 'import PySide6.QtQml' 2>/dev/null; then
     sudo pacman -S --needed --noconfirm pyside6 </dev/tty || die "Installing pyside6 failed."
 fi
 
-# Launcher entry (its id also names the app to the desktop portal).
+# Launcher entry (its id also names the app to the desktop portal). The
+# Steamify shortcut's entry has the same id and always starts the newest
+# release: left alone.
 mkdir -p "$APPS"
+grep -q '^X-Steamify-Shortcut=true' "$APPS/steamify-ui.desktop" 2>/dev/null ||
 cat > "$APPS/steamify-ui.desktop" << EOF
 [Desktop Entry]
 Type=Application