Add Docker deployment for mcwaddams.mcp.website

Multi-stage build: Node 22 for Astro build, Caddy 2 Alpine for
static file serving. Reverse-proxied via caddy-docker-proxy.

docker-compose.yml

@@ -0,0 +1,19 @@
+services:
+  site:
+    build: .
+    restart: unless-stopped
+    networks:
+      - caddy
+    labels:
+      caddy: ${DOMAIN}
+      caddy.reverse_proxy: "{{upstreams 8080}}"
+    healthcheck:
+      test: ["CMD", "wget", "-qO-", "http://127.0.0.1:8080/health"]
+      interval: 30s
+      timeout: 3s
+      start_period: 5s
+      retries: 3
+
+networks:
+  caddy:
+    external: true