clean up duplicated code in installation of desktop services

dist/linux/app.desktop.in

@@ -1,6 +1,6 @@
 [Desktop Entry]
 Version=1.0
-Name=Ghostty@@NAME@@
+Name=@@NAME@@
 Type=Application
 Comment=A terminal emulator
 TryExec=@@GHOSTTY@@
@@ -9,7 +9,7 @@ Icon=com.mitchellh.ghostty
 Categories=System;TerminalEmulator;
 Keywords=terminal;tty;pty;
 StartupNotify=true
-StartupWMClass=com.mitchellh.ghostty@@DEBUG@@
+StartupWMClass=@@APPID@@
 Terminal=false
 Actions=new-window;
 X-GNOME-UsesNotifications=true

dist/linux/com.mitchellh.ghostty.metainfo.xml.in

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <component type="desktop-application">
-  <id>com.mitchellh.ghostty@@DEBUG@@</id>
-  <launchable type="desktop-id">com.mitchellh.ghostty@@DEBUG@@.desktop</launchable>
+  <id>@@APPID@@</id>
+  <launchable type="desktop-id">@@APPID@@.desktop</launchable>
   <name>Ghostty</name>
   <url type="homepage">https://ghostty.org</url>
   <url type="help">https://ghostty.org/docs</url>

dist/linux/dbus.service.in

@@ -1,4 +1,4 @@
 [D-BUS Service]
-Name=com.mitchellh.ghostty@@DEBUG@@
-SystemdService=com.mitchellh.ghostty@@DEBUG@@.service
+Name=@@APPID@@
+SystemdService=@@APPID@@.service
 Exec=@@GHOSTTY@@ --launched-from=dbus

dist/linux/systemd.service.in

@@ -1,7 +1,7 @@
 [Unit]
-Description=Ghostty@@NAME@@
+Description=@@NAME@@
 
 [Service]
 Type=dbus
-BusName=com.mitchellh.ghostty@@DEBUG@@
+BusName=@@APPID@@
 ExecStart=@@GHOSTTY@@ --launched-from=systemd