fix: use Alpine-compatible addgroup/adduser flags in Dockerfiles

Replace --system/--gid/--uid (Debian syntax) with -S/-g/-u (BusyBox/Alpine).
Coolify ARG injection causes exit code 255 with Debian-style flags.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

developer-portal/Dockerfile

@@ -27,8 +27,8 @@ WORKDIR /app
 ENV NODE_ENV=production
 
 # Create non-root user
-RUN addgroup --system --gid 1001 nodejs
-RUN adduser --system --uid 1001 nextjs
+RUN addgroup -S -g 1001 nodejs
+RUN adduser -S -u 1001 -G nodejs nextjs
 
 # Copy built assets
 COPY --from=builder /app/public ./public