feat: add docker health check

cmd/hp_healthcheck/hp_healthcheck.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+)
+
+func main() {
+	client := http.Client{
+		Timeout: 5 * time.Second,
+	}
+
+	resp, err := client.Get("http://localhost:3000/admin/healthz")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Health check failed: %v\n", err)
+		os.Exit(1)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		fmt.Fprintf(os.Stderr, "Health check returned non-OK status: %d\n", resp.StatusCode)
+		os.Exit(1)
+	}
+
+	fmt.Println("Health check passed.")
+	os.Exit(0)
+}