Add Docker infrastructure with caddy-docker-proxy

Multi-stage Dockerfile (node build → caddy:2-alpine production, node dev).
Compose base + dev override for prod/dev switching via .env ENVIRONMENT flag.
Makefile targets: build, up, down, restart, logs, dev, prod, clean, rebuild.
Caddyfile serves static Astro output with caching and compression.

Makefile

@@ -0,0 +1,59 @@
+include .env
+export
+
+# Compose file selection based on ENVIRONMENT
+ifeq ($(ENVIRONMENT),dev)
+  COMPOSE_FILES := -f docker-compose.yml -f docker-compose.dev.yml
+else
+  COMPOSE_FILES := -f docker-compose.yml
+endif
+
+DC := docker compose $(COMPOSE_FILES)
+
+.PHONY: help build up down restart logs status clean rebuild dev prod
+
+help: ## Show this help
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | \
+		awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-15s\033[0m %s\n", $$1, $$2}'
+
+build: ## Build container image
+	$(DC) build
+
+up: ## Start services (detached)
+	$(DC) up -d --build
+	@sleep 2
+	$(DC) logs --tail=20
+
+down: ## Stop services
+	$(DC) down
+
+restart: ## Restart services
+	$(DC) down
+	$(DC) up -d --build
+	@sleep 2
+	$(DC) logs --tail=20
+
+logs: ## Show service logs
+	$(DC) logs -f
+
+status: ## Show running containers
+	$(DC) ps
+
+clean: ## Remove containers, images, and volumes
+	$(DC) down --rmi local -v
+
+rebuild: ## Full rebuild (no cache)
+	$(DC) build --no-cache
+	$(DC) up -d
+	@sleep 2
+	$(DC) logs --tail=20
+
+dev: ## Switch to dev mode and start
+	@sed -i 's/^ENVIRONMENT=.*/ENVIRONMENT=dev/' .env
+	@echo "Switched to dev mode"
+	$(MAKE) restart
+
+prod: ## Switch to prod mode and start
+	@sed -i 's/^ENVIRONMENT=.*/ENVIRONMENT=prod/' .env
+	@echo "Switched to prod mode"
+	$(MAKE) restart