docs: добавить LLM-переменные в .env.example и docker-compose.yml

- .env.example: LLM_ENABLED, LLM_API_BASE, LLM_API_KEY, LLM_MODEL, LLM_TIMEOUT_SECONDS
- docker-compose.yml: прокидывает LLM-переменные в контейнер guarddog-nexus

docker-compose.yml

@@ -7,11 +7,15 @@ services:
       NEXUS_URL: http://nexus:8081
       NEXUS_USERNAME: admin
       NEXUS_PASSWORD: "${NEXUS_PASSWORD:-admin123}"
-      NEXUS_REPOSITORIES: pypi-proxy
       LOG_LEVEL: INFO
       LOG_SYSLOG_HOST: ""
       HOST: "0.0.0.0"
       PORT: "8080"
+      LLM_ENABLED: "${LLM_ENABLED:-0}"
+      LLM_API_BASE: "${LLM_API_BASE:-https://api.openai.com/v1}"
+      LLM_API_KEY: "${LLM_API_KEY:-}"
+      LLM_MODEL: "${LLM_MODEL:-gpt-4o-mini}"
+      LLM_TIMEOUT_SECONDS: "${LLM_TIMEOUT_SECONDS:-30}"
     volumes:
       - ./data:/data
     depends_on: