feat(TrafficRoutes, App): implement interface speed test route and UI integration; update error handling for interface measurement

backend/routes/trafficRoutes.js

@@ -235,9 +235,7 @@ async function measureInterfaceSpeed(req, res) {
           String(i.name).trim() === String(interfaceName).trim()
       );
       if (!iface) {
-        throw new Error(
-          `Интерфейс "${interfaceName}" не найден на RouterOS (${serverId})`
-        );
+        return null;
       }
       const rx =
         iface['rx-byte'] != null
@@ -253,9 +251,17 @@ async function measureInterfaceSpeed(req, res) {
       };
     }
 
+    const notFoundMessage = `Интерфейс "${interfaceName}" не найден на RouterOS (${serverId})`;
+
     const start = await readOne();
+    if (!start) {
+      return sendError(res, 400, notFoundMessage, 'E_IFACE_NOT_FOUND');
+    }
     await sleep(durationSeconds * 1000);
     const end = await readOne();
+    if (!end) {
+      return sendError(res, 400, notFoundMessage, 'E_IFACE_NOT_FOUND');
+    }
 
     const rxBytesDelta = Math.max(0, (end.rxBytes || 0) - (start.rxBytes || 0));
     const txBytesDelta = Math.max(0, (end.txBytes || 0) - (start.txBytes || 0));