Merge monitoring_service training metrics into trading_service system health
monitoring.proto. All 11 proto files now in one canonical location.
Merged monitoring.proto has 13 RPCs (10 system + 3 training) with all
message types from both source protos preserved. Added cpu_percent,
memory_used_mb, memory_total_mb fields to GetLiveTrainingMetricsResponse.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
