refactor: remove batch mode, simplify to API-only deployment

Removes dual-mode deployment complexity, focusing on REST API service only.

Changes:
- Removed batch mode from docker-compose.yml (now single ai-trader service)
- Deleted scripts/test_batch_mode.sh validation script
- Renamed entrypoint-api.sh to entrypoint.sh (now default)
- Simplified Dockerfile (single entrypoint, removed CMD)
- Updated validation scripts to use 'ai-trader' service name
- Updated documentation (README.md, TESTING_GUIDE.md, CHANGELOG.md)

Benefits:
- Eliminates port conflicts between batch and API services
- Simpler configuration and deployment
- API-first architecture aligned with Windmill integration
- Reduced maintenance complexity

Breaking Changes:
- Batch mode no longer available
- All simulations must use REST API endpoints

Dockerfile

@@ -24,8 +24,8 @@ RUN mkdir -p /app/scripts && \
 # Create necessary directories
 RUN mkdir -p data logs data/agent_data
 
-# Make entrypoints executable
-RUN chmod +x entrypoint.sh entrypoint-api.sh
+# Make entrypoint executable
+RUN chmod +x entrypoint.sh
 
 # Expose MCP service ports, API server, and web dashboard
 EXPOSE 8000 8001 8002 8003 8080 8888
@@ -33,6 +33,5 @@ EXPOSE 8000 8001 8002 8003 8080 8888
 # Set Python to run unbuffered for real-time logs
 ENV PYTHONUNBUFFERED=1
 
-# Use entrypoint script
+# Use API entrypoint script (no CMD needed - FastAPI runs as service)
 ENTRYPOINT ["./entrypoint.sh"]
-CMD ["configs/default_config.json"]