Adiciona infra de deploy: Dockerfile multi-stage + nginx + .dockerignore

- Dockerfile: build com Node 20 (vite build) -> serve com nginx alpine
- nginx.conf: SPA routing, cache de assets versionados, healthcheck
- .dockerignore: exclui node_modules, dist e configs de IDE do contexto

.dockerignore

@@ -0,0 +1,13 @@
+node_modules
+dist
+dist-ssr
+.git
+.gitignore
+README.md
+.vscode
+.idea
+.DS_Store
+*.local
+.env
+.env.*
+.vite