Add localPatterns for /api/assets and writable cache dir

- Configure images.localPatterns to allow /api/assets/** with query strings
- Add /app/.next/cache as tmpfs for image optimization cache (read-only container)

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

frontend/docker-compose.yml

@@ -24,6 +24,7 @@ services:
     read_only: true
     tmpfs:
       - /tmp
+      - /app/.next/cache
     cap_drop:
       - ALL
     security_opt:

frontend/next.config.ts

@@ -3,6 +3,12 @@ import type { NextConfig } from "next";
 const nextConfig: NextConfig = {
   output: 'standalone',
   images: {
+    localPatterns: [
+      {
+        pathname: '/api/assets/**',
+        search: '',
+      },
+    ],
     remotePatterns: [
       {
         protocol: 'https',