docker: expose NEXT_PUBLIC_* build args as ENV so Next.js inlines them in client bundle (GA + Supabase + site URL)

Dockerfile

@@ -1,5 +1,18 @@
 FROM node:22-alpine
 WORKDIR /app
+
+# Expose build-time NEXT_PUBLIC_* vars to `npm run build` so Next.js
+# inlines them into the client bundle. Coolify supplies these as
+# --build-arg from app env vars (is_buildtime=true).
+ARG NEXT_PUBLIC_SUPABASE_URL
+ARG NEXT_PUBLIC_SUPABASE_ANON_KEY
+ARG NEXT_PUBLIC_SITE_URL
+ARG NEXT_PUBLIC_GA_MEASUREMENT_ID
+ENV NEXT_PUBLIC_SUPABASE_URL=$NEXT_PUBLIC_SUPABASE_URL
+ENV NEXT_PUBLIC_SUPABASE_ANON_KEY=$NEXT_PUBLIC_SUPABASE_ANON_KEY
+ENV NEXT_PUBLIC_SITE_URL=$NEXT_PUBLIC_SITE_URL
+ENV NEXT_PUBLIC_GA_MEASUREMENT_ID=$NEXT_PUBLIC_GA_MEASUREMENT_ID
+
 COPY package*.json ./
 RUN npm install
 COPY . .