Deprecate Alpine-based Dockerfile to prevent glibc compatibility issues

Changes:
- Renamed Dockerfile.simple → Dockerfile.simple.DEPRECATED
- Added prominent warning about Alpine/musl libc incompatibility
- Updated Makefile docker-agent target to use Dockerfile.ubuntu
- Added production deployment notes in Makefile
- Updated docker-compose.yml with LightRAG environment variables

Reason:
The chorus-agent binary built with 'make build-agent' is linked against
glibc and cannot run on Alpine's musl libc. This causes the runtime error:
"exec /app/chorus-agent: no such file or directory"

Production deployments MUST use Dockerfile.ubuntu for glibc compatibility.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docker/docker-compose.yml

@@ -56,7 +56,14 @@ services:
       # Model configuration
       - CHORUS_MODELS=${CHORUS_MODELS:-meta/llama-3.1-8b-instruct}
       - CHORUS_DEFAULT_REASONING_MODEL=${CHORUS_DEFAULT_REASONING_MODEL:-meta/llama-3.1-8b-instruct}
-      
+
+      # LightRAG configuration (optional RAG enhancement)
+      - CHORUS_LIGHTRAG_ENABLED=${CHORUS_LIGHTRAG_ENABLED:-false}
+      - CHORUS_LIGHTRAG_BASE_URL=${CHORUS_LIGHTRAG_BASE_URL:-http://lightrag:9621}
+      - CHORUS_LIGHTRAG_TIMEOUT=${CHORUS_LIGHTRAG_TIMEOUT:-30s}
+      - CHORUS_LIGHTRAG_API_KEY=${CHORUS_LIGHTRAG_API_KEY:-}
+      - CHORUS_LIGHTRAG_DEFAULT_MODE=${CHORUS_LIGHTRAG_DEFAULT_MODE:-hybrid}
+
       # Logging configuration
       - LOG_LEVEL=${LOG_LEVEL:-info}
       - LOG_FORMAT=${LOG_FORMAT:-structured}