대시보드 시스템 상태 카드에 메모리·디스크 신호등 추가

- Backend: PipelineMonitorService에 system 항목 추가 (OS 메모리, 디스크 사용률)
- Frontend: SystemMonitorDto에 system 필드 추가
- DashboardPage: 시스템/메모리/디스크 3열 신호등 레이아웃 적용
- dashboardCommand.css: gc-dash-sys-status, gc-sys-tl-item 스타일 추가

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/main/java/com/goldenchart/trading/pipeline/PipelineMonitorService.java

@@ -5,6 +5,7 @@ import com.goldenchart.websocket.UpbitWebSocketClient;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 
+import java.io.File;
 import java.lang.management.ManagementFactory;
 import java.lang.management.MemoryMXBean;
 import java.lang.management.ThreadInfo;
@@ -62,6 +63,7 @@ public class PipelineMonitorService {
                 "gapBackfillCron", props.getGapBackfillCron()
         ));
         out.put("jvm", jvmMetrics());
+        out.put("system", systemMetrics());
         out.put("traffic", computeTrafficRates());
         out.put("memory", ta4jStorage.storageMetrics());
         out.put("queue", eventQueue.stats());
@@ -91,6 +93,40 @@ public class PipelineMonitorService {
         return m;
     }
 
+    private Map<String, Object> systemMetrics() {
+        Map<String, Object> m = new LinkedHashMap<>();
+        // OS 물리 메모리
+        try {
+            com.sun.management.OperatingSystemMXBean osMx =
+                    (com.sun.management.OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
+            long totalPhys = osMx.getTotalMemorySize();
+            long freePhys  = osMx.getFreeMemorySize();
+            double memPct  = totalPhys > 0 ? (totalPhys - freePhys) * 100.0 / totalPhys : 0;
+            m.put("osMemUsedMb",  roundMb(totalPhys - freePhys));
+            m.put("osMemTotalMb", roundMb(totalPhys));
+            m.put("osMemPct",     Math.round(memPct * 10) / 10.0);
+        } catch (Exception e) {
+            m.put("osMemUsedMb", 0);
+            m.put("osMemTotalMb", 0);
+            m.put("osMemPct", 0.0);
+        }
+        // 디스크 (루트 파티션)
+        try {
+            File root = new File("/");
+            long total = root.getTotalSpace();
+            long free  = root.getFreeSpace();
+            double diskPct = total > 0 ? (total - free) * 100.0 / total : 0;
+            m.put("diskUsedGb",  Math.round((total - free) / 1073741824.0 * 10) / 10.0);
+            m.put("diskTotalGb", Math.round(total / 1073741824.0 * 10) / 10.0);
+            m.put("diskPct",     Math.round(diskPct * 10) / 10.0);
+        } catch (Exception e) {
+            m.put("diskUsedGb", 0.0);
+            m.put("diskTotalGb", 0.0);
+            m.put("diskPct", 0.0);
+        }
+        return m;
+    }
+
     private Map<String, Object> computeTrafficRates() {
         long now = System.currentTimeMillis();
         var q = eventQueue.stats();