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

CHANGELOG.md

@@ -7,6 +7,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- **Simplified Deployment** - Removed batch mode, now API-only
+  - Single docker-compose service (ai-trader) instead of dual mode
+  - Removed scripts/test_batch_mode.sh
+  - Streamlined entrypoint (entrypoint.sh now runs API server)
+  - Simplified docker-compose.yml configuration
+
+### Removed
+- **Batch Mode** - Eliminated one-time batch simulation mode
+  - All simulations now run through REST API
+  - Removes complexity of dual-mode deployment
+  - Focus on API-first architecture for Windmill integration
+
 ## [0.3.0] - 2025-10-31
 
 ### Added - API Service Transformation