Add Dockerfile and docker-compose for production deployment

Multi-stage build: Node 20 builds the React app, nginx serves the static files on port 3000.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DReRqHxSYuVfCzTzQGD9hZ

docker-compose.yml

@@ -0,0 +1,5 @@
+services:
+  prayer:
+    build: .
+    ports:
+      - "3000:80"