fix(docker): fix standalone output path in frontend Dockerfile

Next.js 16 standalone output preserves monorepo subdirectory
structure, placing server.js at frontend/server.js instead of
server.js. Updated COPY paths and CMD to match.

frontend/Dockerfile

@@ -36,8 +36,8 @@ WORKDIR /app
 
 # Copy standalone output
 COPY --from=builder /app/frontend/.next/standalone ./
-COPY --from=builder /app/frontend/.next/static ./.next/static
-COPY --from=builder /app/frontend/public ./public
+COPY --from=builder /app/frontend/.next/static ./frontend/.next/static
+COPY --from=builder /app/frontend/public ./frontend/public
 
 # Expose port
 EXPOSE 3000
@@ -46,4 +46,4 @@ ENV PORT=3000
 ENV HOSTNAME="0.0.0.0"
 
 # Start application
-CMD ["node", "server.js"]
+CMD ["node", "frontend/server.js"]