feat: ui rework and gear generator

lib/service/shifter_service.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 
 import 'package:abawo_bt_app/controller/bluetooth.dart';
+import 'package:abawo_bt_app/model/gear_ratio_codec.dart';
 import 'package:abawo_bt_app/model/shifter_types.dart';
 import 'package:anyhow/anyhow.dart';
 import 'package:logging/logging.dart';
@@ -43,7 +44,6 @@ class ShifterService {
   static const int _gearRatioSlots = 32;
   static const int _defaultGearIndexOffset = _gearRatioSlots;
   static const int _gearRatioPayloadBytes = _gearRatioSlots + 1;
-  static const double _maxGearRatio = 255 / 64;
   static const int _gearRatioWriteMtu = 64;
 
   Future<Result<void>> writeConnectToAddress(String bikeDeviceId) async {
@@ -166,12 +166,61 @@ class ShifterService {
     }
 
     try {
-      return Ok(CentralStatus.fromCborBytes(readRes.unwrap()));
+      return Ok(CentralStatus.fromBytes(readRes.unwrap()));
     } catch (e) {
       return bail('Failed to decode status payload: $e');
     }
   }
 
+  Future<Result<ShifterDeviceTelemetry>> readDeviceTelemetry() async {
+    int? batteryPercent;
+    String? firmwareRevision;
+    final errors = <String>[];
+
+    final batteryResult = await _requireBluetooth.readCharacteristic(
+      buttonDeviceId,
+      batteryServiceUuid,
+      batteryLevelCharacteristicUuid,
+    );
+    if (batteryResult.isOk()) {
+      try {
+        batteryPercent = parseBatteryLevelPercent(batteryResult.unwrap());
+      } catch (error) {
+        errors.add('battery parse failed: $error');
+      }
+    } else {
+      errors.add('battery read failed: ${batteryResult.unwrapErr()}');
+    }
+
+    final firmwareResult = await _requireBluetooth.readCharacteristic(
+      buttonDeviceId,
+      deviceInformationServiceUuid,
+      firmwareRevisionCharacteristicUuid,
+    );
+    if (firmwareResult.isOk()) {
+      try {
+        firmwareRevision = parseGattUtf8String(firmwareResult.unwrap());
+      } catch (error) {
+        errors.add('firmware parse failed: $error');
+      }
+    } else {
+      errors.add('firmware read failed: ${firmwareResult.unwrapErr()}');
+    }
+
+    if (batteryPercent == null &&
+        firmwareRevision == null &&
+        errors.isNotEmpty) {
+      return bail('Could not read battery or firmware: ${errors.join('; ')}');
+    }
+
+    return Ok(
+      ShifterDeviceTelemetry(
+        batteryPercent: batteryPercent,
+        firmwareRevision: firmwareRevision,
+      ),
+    );
+  }
+
   Future<Result<DfuPreflightResult>> runDfuPreflight({
     int requestedMtu = universalShifterDfuPreferredMtu,
   }) async {
@@ -253,7 +302,7 @@ class ShifterService {
           .listen(
         (data) {
           try {
-            final status = CentralStatus.fromCborBytes(data);
+            final status = CentralStatus.fromBytes(data);
             _statusController.add(status);
           } catch (error, st) {
             _log.warning(
@@ -284,19 +333,11 @@ class ShifterService {
   }
 
   int _encodeGearRatio(double value) {
-    if (value <= 0) {
-      return 0;
-    }
-    final clamped = value.clamp(0, _maxGearRatio);
-    final scaled = (clamped * 64).round();
-    if (scaled <= 0) {
-      return 1;
-    }
-    return scaled.clamp(1, 255);
+    return encodeGearRatioByte(value);
   }
 
   double _decodeGearRatio(int raw) {
-    return raw / 64.0;
+    return decodeGearRatioByte(raw);
   }
 
   String _formatBytes(List<int> bytes) {