feat(api_gateway): populate ServiceStatus.version from build_info

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

services/api_gateway/src/grpc/monitoring_handler.rs

@@ -284,6 +284,7 @@ impl MonitoringServiceHandler {
                     health: ServiceHealth::Unhealthy.into(),
                     state: ServiceState::Error.into(),
                     error_message: Some(format!("Invalid URL: {url}")),
+                    version: Some(common::build_info::version().to_owned()),
                     ..Default::default()
                 };
             }
@@ -333,6 +334,7 @@ impl MonitoringServiceHandler {
             health: health.into(),
             state: state.into(),
             error_message: msg,
+            version: Some(common::build_info::version().to_owned()),
             last_health_check: now,
             uptime_seconds: uptime_secs,
             metadata,