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"]