chore: restructure project into backend and frontend folders

- Move all frontend code to frontend/ directory
- Add backend/ with Go project structure (cmd, internal, pkg)
- Add docker-compose.yml for orchestration

docker-compose.yml

@@ -0,0 +1,28 @@
+services:
+  # Development service with hot reload
+  frontend-dev:
+    image: node:20-alpine
+    working_dir: /app
+    volumes:
+      - ./frontend:/app
+      - node_modules:/app/node_modules
+    ports:
+      - "5173:5173"
+    environment:
+      - NODE_ENV=development
+    command: sh -c "yarn install && yarn dev --host"
+    stdin_open: true
+    tty: true
+
+  # Production frontend service
+  frontend:
+    build:
+      context: ./frontend
+      dockerfile: Dockerfile
+      target: production
+    ports:
+      - "8080:80"
+    restart: unless-stopped
+
+volumes:
+  node_modules: