fix: add /api/obd/status endpoint, dashboard OBD fallback on page load, fix GPS string-to-number crash

app.py

@@ -139,6 +139,15 @@ def trips():
 def gps_status():
     return jsonify(app_gps.get_status())
 
+@app.route('/api/obd/status')
+def obd_status():
+    return jsonify({
+        "adapter_present": bool(app_obd._find_obd_port()),
+        "port": app_obd._find_obd_port(),
+        "car_connected": app_obd._is_car_connected(),
+        "status_label": "Connected" if app_obd._is_car_connected() else "Disconnected",
+    })
+
 @app.route('/api/trip/<int:trip_id>')
 def trip_route(trip_id):
     trip = app_sql.get_trip_route(trip_id)