fixes and improvements

backend/src/media_library_viewer_api/routers/dashboard.py

@@ -44,7 +44,32 @@ def get_monitoring_overview(
 ) -> dict[str, Any]:
     """Return one lightweight monitoring row per configured machine."""
     machines = store.list_machines()
-    rows = [collect_machine_overview(machine, store) for machine in machines]
+    rows: list[dict[str, Any]] = []
+    for machine in machines:
+        try:
+            rows.append(collect_machine_overview(machine, store))
+        except Exception as exc:
+            logger.exception(
+                "Dashboard monitoring overview failed for machine_id=%s",
+                machine.get("id"),
+            )
+            rows.append({
+                "machine": {k: machine.get(k) for k in ("id", "name", "mode", "enabled", "host", "port", "username", "media_root", "path_prefix", "notes")},
+                "status": "",
+                "status_error": str(exc),
+                "metrics_error": str(exc),
+                "disk_error": str(exc),
+                "sample_count": 0,
+                "latest_sample": None,
+                "cpu_summary": None,
+                "iowait_summary": None,
+                "mem_summary": None,
+                "net_rx_summary": None,
+                "net_tx_summary": None,
+                "disk_read_summary": None,
+                "disk_write_summary": None,
+                "disk": None,
+            })
     poller = get_monitoring_poller().snapshot()
     enabled_count = sum(1 for machine in machines if machine.get("enabled"))
     logger.info("Dashboard monitoring machines=%s enabled=%s", len(machines), enabled_count)