Remove bufsize=1 from sensor subprocess

Line buffering only works with text mode, not binary pipes.
Fixes RuntimeWarning about line buffering.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

routes/sensor.py

@@ -130,8 +130,7 @@ def start_sensor() -> Response:
             app_module.sensor_process = subprocess.Popen(
                 cmd,
                 stdout=subprocess.PIPE,
-                stderr=subprocess.PIPE,
+                stderr=subprocess.PIPE
-                bufsize=1
             )
 
             # Start output thread