Fix: Pass APP_SECRET to container for stable sessions

compose/docker-compose.yml

@@ -6,6 +6,7 @@ services:
     environment:
       - DATABASE_URL=mysql+pymysql://$MARIADB_USER:$MARIADB_PASSWORD@db:3306/$MARIADB_DATABASE
       - SECRET_KEY=${SECRET_KEY}
+      - APP_SECRET=${APP_SECRET}
       - OPENAI_API_KEY=${OPENAI_API_KEY}
       - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY}
       - OPENROUTER_API_KEY=${OPENROUTER_API_KEY}