Fix repeater battery % inconsistency and add configurable repeater battery chemistry (#199)

* fix(repeater): unify battery percentage math and add repeater chemistry setting

- Add shared battery percent utility used by connector, repeater status, and telemetry

- Add repeater-specific battery chemistry persistence and service accessors

- Add repeater chemistry selector in Repeater Hub

- Ensure telemetry and status compute percentages consistently from same chemistry

- Add focused battery utility tests

Refs #116

Refs #174

* fix: Flutter Analyzer Errors fixed Recent Merge Compatible

* Unify repeater battery source across status and telemetry

lib/services/app_settings_service.dart

@@ -17,6 +17,12 @@ class AppSettingsService extends ChangeNotifier {
     return stored ?? 'nmc';
   }
 
+  String batteryChemistryForRepeater(String repeaterPubKeyHex) {
+    final stored = _settings.batteryChemistryByRepeaterId[repeaterPubKeyHex];
+    if (stored == 'liion') return 'nmc';
+    return stored ?? 'nmc';
+  }
+
   Future<void> loadSettings() async {
     final prefs = PrefsManager.instance;
     final jsonStr = prefs.getString(_settingsKey);
@@ -133,13 +139,20 @@ class AppSettingsService extends ChangeNotifier {
     );
   }
 
+  Future<void> setBatteryChemistryForRepeater(
+    String repeaterPubKeyHex,
+    String chemistry,
+  ) async {
+    final updated = Map<String, String>.from(
+      _settings.batteryChemistryByRepeaterId,
+    );
+    updated[repeaterPubKeyHex] = chemistry;
+    await updateSettings(
+      _settings.copyWith(batteryChemistryByRepeaterId: updated),
+    );
+  }
+
   Future<void> setUnitSystem(UnitSystem value) async {
     await updateSettings(_settings.copyWith(unitSystem: value));
   }
-
-  Future<void> setLosUnitSystem(String value) async {
-    await setUnitSystem(
-      value == 'imperial' ? UnitSystem.imperial : UnitSystem.metric,
-    );
-  }
 }