Initial commit: Sudoku game with accounts, history, leaderboard, themes and i18n

Node/Express + SQLite backend, vanilla JS frontend, deployed via Docker Compose.

docker-compose.yml

@@ -0,0 +1,13 @@
+services:
+  sudoku:
+    build: .
+    container_name: sudoku
+    restart: unless-stopped
+    ports:
+      - "8090:3000"
+    environment:
+      - NODE_ENV=production
+      - JWT_SECRET=${JWT_SECRET}
+    volumes:
+      - ./app:/app/public:ro
+      - ./data:/app/data