fix(meshcore): call scan_ble_sync() not scan_ble() in ble/scan route

Route was calling a non-existent method, causing a 500 on every scan.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

routes/meshcore.py

@@ -93,7 +93,7 @@ def ports():
 def ble_scan():
     if not is_meshcore_available():
         return api_error("meshcore not installed", 503)
-    devices = _client().scan_ble()
+    devices = _client().scan_ble_sync()
     return jsonify({"devices": devices})