Add systemd user service and CLI wrapper for remote-touchpad

This commit introduces a complete systemd user service setup for
remote-touchpad, eliminating the need for users to manually manage
the binary process. Key additions:

- New rts CLI wrapper script providing a user-friendly interface
  for service management without requiring root access
- Systemd service file for proper background operation with
  restart policies and dependency management
- Service management commands: install, start, stop, status,
  restart, and uninstall
- URL extraction and QR code generation via the url command
- Service log viewing via the log command

The installation process now:
1. Verifies Go is installed
2. Builds the remote-touchpad binary with appropriate tags
3. Installs service files to ~/.config/systemd/user/
4. Installs the binary to ~/.local/bin/
5. Enables and starts the service automatically

The README has been updated with comprehensive installation
instructions for the new user service approach.

remote-touchpad.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Remote Touchpad Service
+After=network.target
+
+[Service]
+Type=simple
+ExecStart=%h/.local/bin/remote-touchpad
+Restart=always
+RestartSec=5s
+
+[Install]
+WantedBy=default.target