fix(paths): use _get_dm() instead of nonexistent cli.get_device_manager()

The reset_flood endpoint was calling cli.get_device_manager() which
doesn't exist. All other endpoints use the local _get_dm() helper.

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

app/routes/api.py

@@ -2315,7 +2315,7 @@ def reorder_contact_paths(pubkey):
 def reset_contact_to_flood(pubkey):
     """Reset device path to FLOOD mode (does not delete configured paths)."""
     try:
-        dm = cli.get_device_manager()
+        dm = _get_dm()
         if not dm or not dm.is_connected:
             return jsonify({'success': False, 'error': 'Device not connected'}), 503
         dev_result = dm.reset_path(pubkey)