feat(client): add nginx config for SPA routing and API proxy

- add try_files fallback to serve index.html for all non-asset paths
- proxy /api/ requests to the server container to avoid HTML being
  returned by nginx for API calls when using full route paths

client/Dockerfile

@@ -15,5 +15,6 @@ RUN npm run -w client build
 FROM nginx:alpine AS runtime
 
 COPY --from=builder /app/client/dist /usr/share/nginx/html
+COPY client/nginx.conf /etc/nginx/conf.d/default.conf
 
 EXPOSE 80