Add Docker deployment with automatic HTTPS

A two-stage image runs the tests and builds the game with Node, then
serves dist/ with Caddy, which obtains and renews Let's Encrypt
certificates for robotmarkets.ir (configurable via SITE_ADDRESS).
HTTPS is required for installing the PWA and for GPS mode.

- Caddyfile: gzip/zstd, long-lived caching for hashed assets, no-cache
  for the page, service worker and manifest, SPA fallback, permissions
  policy for location and motion sensors
- docker-compose.yml: ports 80/443, persistent certificate volumes
- README: server setup, updates, running behind an existing proxy, and
  workarounds when Docker Hub is unreachable from servers in Iran

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,7 @@
+node_modules
+dist
+.git
+.github
+.idea
+.claude
+*.log