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>

.gitignore

@@ -0,0 +1,30 @@
+# Dependencies
+node_modules/
+
+# Build
+.next/
+out/
+dist/
+
+# Environment
+.env
+.env.local
+.env.*.local
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Go
+backend/main
+*.exe
+
+# Logs
+*.log
+npm-debug.log*