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.

docker-compose.yml

@@ -0,0 +1,16 @@
+services:
+  docs:
+    build:
+      context: .
+      target: production
+      dockerfile: Dockerfile
+    restart: unless-stopped
+    networks:
+      - caddy
+    labels:
+      caddy: ${DOMAIN}
+      caddy.reverse_proxy: "{{upstreams 80}}"
+
+networks:
+  caddy:
+    external: true