feat: ui rework and gear generator

lib/controller/shifter_device_telemetry.dart

@@ -0,0 +1,20 @@
+import 'package:abawo_bt_app/model/shifter_types.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+final shifterDeviceTelemetryCacheProvider = StateNotifierProvider<
+    ShifterDeviceTelemetryCache, Map<String, ShifterDeviceTelemetry>>(
+  (ref) => ShifterDeviceTelemetryCache(),
+);
+
+class ShifterDeviceTelemetryCache
+    extends StateNotifier<Map<String, ShifterDeviceTelemetry>> {
+  ShifterDeviceTelemetryCache() : super(const {});
+
+  void upsert(String deviceId, ShifterDeviceTelemetry telemetry) {
+    final existing = state[deviceId];
+    state = {
+      ...state,
+      deviceId: existing == null ? telemetry : existing.merge(telemetry),
+    };
+  }
+}