fix(#65): scan BLE by NUS service UUID instead of name prefix

The scanner filtered advertisements by device-name keyword
(withKeywords: deviceNamePrefixes), so any MeshCore/Offband device
whose advertised name fell outside the hardcoded prefix list was
invisible to the scanner — even though the official MeshCore app,
which scans by the Nordic UART service UUID, found them. Switch
startScan to withServices: [Guid(service)] and drop the now-redundant
name filter on the already-service-scoped systemDevices fallback.

Device-tested on a Samsung S25: a previously-invisible node now
appears in the scan.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/connector/meshcore_connector.dart

@@ -1435,7 +1435,7 @@ class MeshCoreConnector extends ChangeNotifier {
 
     try {
       await FlutterBluePlus.startScan(
-        withKeywords: MeshCoreUuids.deviceNamePrefixes,
+        withServices: [Guid(MeshCoreUuids.service)],
         webOptionalServices: [Guid(MeshCoreUuids.service)],
         timeout: timeout,
         androidScanMode: AndroidScanMode.lowLatency,
@@ -1459,11 +1459,6 @@ class MeshCoreConnector extends ChangeNotifier {
         ..clear()
         ..addAll(
           systemDevices
-              .where(
-                (device) => MeshCoreUuids.deviceNamePrefixes.any(
-                  device.platformName.startsWith,
-                ),
-              )
               .map(
                 (device) => ScanResult(
                   device: device,