Add version subcommand and Makefile semver bump targets

- var version injected at build time via -X main.version=$(VERSION)
- VERSION derives from 'git describe --tags' so built binaries show
  the exact tag (or tag+commits+sha for dirty/untagged builds)
- 'make patch/minor/major' reads the latest vX.Y.Z tag and creates
  the next one; starts from v0.0.0 if no tags exist yet

main.go

@@ -25,6 +25,8 @@ const (
 	appName            = "node-lookup"
 )
 
+var version = "dev"
+
 // config holds all configurable values. Fields map 1:1 to config file keys,
 // env vars (NODE_LOOKUP_*), and (where applicable) CLI flags.
 type config struct {
@@ -397,6 +399,14 @@ func main() {
 	configCmd.AddCommand(configInitCmd, configShowCmd)
 	rootCmd.AddCommand(configCmd)
 
+	versionCmd := &cobra.Command{
+		Use:          "version",
+		Short:        "Print the version",
+		Run:          func(cmd *cobra.Command, args []string) { fmt.Println(version) },
+		SilenceUsage: true,
+	}
+	rootCmd.AddCommand(versionCmd)
+
 	if err := rootCmd.Execute(); err != nil {
 		os.Exit(1)
 	}