Add full-stack Hello World app with CI/CD

- Go backend with PostgreSQL connection
- Next.js frontend with TypeScript
- Docker Compose for local development
- Woodpecker CI pipeline for build and push
- Kubernetes manifests with Kustomize
- ArgoCD application for GitOps deployment

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/Dockerfile

@@ -0,0 +1,19 @@
+FROM golang:1.21-alpine AS builder
+
+WORKDIR /app
+
+COPY go.mod ./
+RUN go mod download
+
+COPY . .
+RUN go mod tidy && CGO_ENABLED=0 GOOS=linux go build -o main .
+
+FROM alpine:latest
+
+WORKDIR /app
+
+COPY --from=builder /app/main .
+
+EXPOSE 8080
+
+CMD ["./main"]

backend/go.mod

@@ -0,0 +1,5 @@
+module hello-world-backend
+
+go 1.21
+
+require github.com/lib/pq v1.10.9

backend/main.go

@@ -0,0 +1,93 @@
+package main
+
+import (
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+
+	_ "github.com/lib/pq"
+)
+
+type Response struct {
+	Message string `json:"message"`
+	DBStatus string `json:"db_status"`
+}
+
+var db *sql.DB
+
+func main() {
+	// PostgreSQL connection
+	dbHost := getEnv("DB_HOST", "localhost")
+	dbPort := getEnv("DB_PORT", "5432")
+	dbUser := getEnv("DB_USER", "postgres")
+	dbPassword := getEnv("DB_PASSWORD", "postgres")
+	dbName := getEnv("DB_NAME", "hellodb")
+
+	connStr := fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=disable",
+		dbHost, dbPort, dbUser, dbPassword, dbName)
+
+	var err error
+	db, err = sql.Open("postgres", connStr)
+	if err != nil {
+		log.Printf("Warning: Could not connect to database: %v", err)
+	} else {
+		defer db.Close()
+	}
+
+	// HTTP handlers
+	http.HandleFunc("/api/hello", corsMiddleware(helloHandler))
+	http.HandleFunc("/api/health", corsMiddleware(healthHandler))
+
+	port := getEnv("PORT", "8080")
+	log.Printf("Server starting on port %s", port)
+	log.Fatal(http.ListenAndServe(":"+port, nil))
+}
+
+func helloHandler(w http.ResponseWriter, r *http.Request) {
+	dbStatus := "disconnected"
+
+	if db != nil {
+		err := db.Ping()
+		if err == nil {
+			dbStatus = "connected"
+		}
+	}
+
+	response := Response{
+		Message:  "Hello World! - Go + PostgreSQL + Next.js",
+		DBStatus: dbStatus,
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(response)
+}
+
+func healthHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
+}
+
+func corsMiddleware(next http.HandlerFunc) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Access-Control-Allow-Origin", "*")
+		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
+		w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
+
+		if r.Method == "OPTIONS" {
+			w.WriteHeader(http.StatusOK)
+			return
+		}
+
+		next(w, r)
+	}
+}
+
+func getEnv(key, defaultValue string) string {
+	if value := os.Getenv(key); value != "" {
+		return value
+	}
+	return defaultValue
+}