fix(typescript): tighten TypeScript null safety and error handling across backend and ops UI

ts/monitoring/classes.metricsmanager.ts

@@ -296,11 +296,11 @@ export class MetricsManager {
       const proxyMetrics = this.dcRouter.smartProxy ? this.dcRouter.smartProxy.getMetrics() : null;
       
       if (!proxyMetrics) {
-        return [];
+        return [] as Array<{ type: string; count: number; source: string; lastActivity: Date }>;
       }
-      
+
       const connectionsByRoute = proxyMetrics.connections.byRoute();
-      const connectionInfo = [];
+      const connectionInfo: Array<{ type: string; count: number; source: string; lastActivity: Date }> = [];
       
       for (const [routeName, count] of connectionsByRoute) {
         connectionInfo.push({