fix: add missing ConnectionMonitor component

The connection-monitor.tsx component was referenced in App.tsx but the
file was missing, causing TypeScript compilation failure during Docker
build. This component combines the useConnectionMonitor hook with
the ConnectionBanner UI.

apps/web/src/components/common/connection-monitor.tsx

@@ -0,0 +1,7 @@
+import { useConnectionMonitor } from "@/hooks/use-connection-monitor";
+import { ConnectionBanner } from "./connection-banner";
+
+export function ConnectionMonitor() {
+  useConnectionMonitor();
+  return <ConnectionBanner />;
+}