Run frontend in production mode instead of exposed npm run dev

next dev bound to 0.0.0.0:3000 with the host source dir bind-mounted
rw was the entry point malware kept getting dropped through (see
prior commit). Now builds and runs `next start`; the bind mount is
gone so a compromised container can no longer write onto host disk.
Also bumps next to 15.1.11, patching CVE-2025-66478 (critical RCE via
the RSC Next-Action header) and the follow-up CVE-2025-67779/55184/
55183 batch — the installed 15.1.6 was vulnerable to all of them and
is the likely actual initial-access vector.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gh2UXUQUVBWroWEnn1FLFG

docker-compose.yml

@@ -34,10 +34,6 @@ services:
     restart: unless-stopped
     env_file:
       - ./frontend/.env.local
-    volumes:
-      - ./frontend:/app
-      - /app/node_modules
-      - /app/.next
     ports:
       - "3000:3000"
     depends_on: