next.config.js: pass basePath from env

Dockerfile

@@ -16,6 +16,7 @@ WORKDIR /app
 COPY --from=deps /app/node_modules ./node_modules
 COPY . .
 
+ARG NEXT_PUBLIC_BASE_PATH
 ARG NEXT_PUBLIC_COLOR_PRIMARY
 ARG NEXT_PUBLIC_COLOR_SECONDARY
 ARG NEXT_PUBLIC_COLOR_TERTIARTY

next.config.js

@@ -6,6 +6,7 @@ const withGraphQL = require('next-plugin-graphql');
 
 /** @type {import('next').NextConfig} */
 const nextConfig = {
+  basePath: process.env.NEXT_PUBLIC_BASE_PATH,
   output: 'standalone',
   swcMinify: true,
   reactStrictMode: true,