feat: add install command for easy deployment

- Add `install` subcommand with alias `i`
- Support two installation methods: systemd (default) and service
- Copy binary to /usr/local/bin/go-alived
- Auto-detect network interface and hostname for config generation
- Create /etc/go-alived directory and config.yaml
- Install systemd service file with proper capabilities
- Display clear completion message with next steps
- Bump version to 1.2.0

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internal/cmd/root.go

@@ -11,7 +11,7 @@ var rootCmd = &cobra.Command{
 	Short: "Go-Alived - VRRP High Availability Service",
 	Long: `go-alived is a lightweight, dependency-free VRRP implementation in Go.
 It provides high availability for IP addresses with health checking support.`,
-	Version: "1.0.0",
+	Version: "1.2.0",
 }
 
 func Execute() {