chore: add Docker deployment behind Caddy

Build the static Next.js export in a reproducible container and expose it
through the existing Caddy network and upstream service name.

compose.yaml

@@ -0,0 +1,15 @@
+services:
+  static-site:
+    image: amiirkhl-portfolio:latest
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: static-site
+    restart: unless-stopped
+    networks:
+      - caddy_proxy
+
+networks:
+  caddy_proxy:
+    external: true
+    name: caddy_proxy