Add mobile sandbox optimizations for v1.5.3

- Skip systemd-resolved initialization on Android (ChromeOS crash fix)
- Skip system DNS discovery commands on iOS mobile (sandbox restrictions)
- Skip route-based DNS discovery on Android
- Skip systemd resolver on Android
- Add mobile platform checks to prevent sandbox access violations

These changes ensure ctrld works correctly in mobile sandboxed environments
where system commands and file access are restricted.

cmd/cli/prog_linux.go

@@ -14,6 +14,9 @@ import (
 )
 
 func init() {
+	if isAndroid() {
+		return
+	}
 	if r, err := newLoopbackOSConfigurator(); err == nil {
 		useSystemdResolved = r.Mode() == "systemd-resolved"
 	}