feat: add Dockerfile for production deployment

Multi-stage build: Node 18 builds the Vite app, nginx serves
the static output. Nginx config proxies /api/ to the backend
container and handles SPA client-side routing with try_files.

Build args VITE_API_BASE_URL and VITE_APP_NAME are configurable
at build time via docker build --build-arg.

Made-with: Cursor

.dockerignore

@@ -0,0 +1,10 @@
+node_modules
+dist
+.git
+.env
+.env.local
+.env.production
+*.md
+docs/
+.vscode/
+coverage/