Added Line Of Sight Feature for repeater placement, Added app wide Units Setting (#198)

* feat: add LOS workflow, global units, l10n cleanup, and mobile UI overflow fixes

Squashes prior PR commits into one changeset including: LOS map/service/tests, global metric/imperial unit system adoption, notification/BLE safety fixes, app-wide localization backfill/mojibake cleanup, and responsive UI title/overflow hardening.

* l10n: revert unrelated locale churn for LOS feature

* feat: keep LOS with app-wide unit settings

* fix: resolve post-merge app bar/import analyzer errors

* style: format screen files for CI

lib/models/app_settings.dart

@@ -1,3 +1,16 @@
+enum UnitSystem { metric, imperial }
+
+extension UnitSystemValue on UnitSystem {
+  String get value {
+    switch (this) {
+      case UnitSystem.imperial:
+        return 'imperial';
+      case UnitSystem.metric:
+        return 'metric';
+    }
+  }
+}
+
 class AppSettings {
   static const Object _unset = Object();
 
@@ -21,6 +34,7 @@ class AppSettings {
   final String? languageOverride; // null = system default
   final bool appDebugLogEnabled;
   final Map<String, String> batteryChemistryByDeviceId;
+  final UnitSystem unitSystem;
 
   AppSettings({
     this.clearPathOnMaxRetry = false,
@@ -43,6 +57,7 @@ class AppSettings {
     this.languageOverride,
     this.appDebugLogEnabled = false,
     Map<String, String>? batteryChemistryByDeviceId,
+    this.unitSystem = UnitSystem.metric,
   }) : batteryChemistryByDeviceId = batteryChemistryByDeviceId ?? {};
 
   Map<String, dynamic> toJson() {
@@ -67,10 +82,18 @@ class AppSettings {
       'language_override': languageOverride,
       'app_debug_log_enabled': appDebugLogEnabled,
       'battery_chemistry_by_device_id': batteryChemistryByDeviceId,
+      'unit_system': unitSystem.value,
     };
   }
 
   factory AppSettings.fromJson(Map<String, dynamic> json) {
+    UnitSystem parseUnitSystem(dynamic value) {
+      if (value is String && value.toLowerCase() == 'imperial') {
+        return UnitSystem.imperial;
+      }
+      return UnitSystem.metric;
+    }
+
     return AppSettings(
       clearPathOnMaxRetry: json['clear_path_on_max_retry'] as bool? ?? false,
       mapShowRepeaters: json['map_show_repeaters'] as bool? ?? true,
@@ -101,6 +124,9 @@ class AppSettings {
             (key, value) => MapEntry(key.toString(), value.toString()),
           ) ??
           {},
+      unitSystem: parseUnitSystem(
+        json['unit_system'] ?? json['los_unit_system'],
+      ),
     );
   }
 
@@ -125,6 +151,7 @@ class AppSettings {
     Object? languageOverride = _unset,
     bool? appDebugLogEnabled,
     Map<String, String>? batteryChemistryByDeviceId,
+    UnitSystem? unitSystem,
   }) {
     return AppSettings(
       clearPathOnMaxRetry: clearPathOnMaxRetry ?? this.clearPathOnMaxRetry,
@@ -154,6 +181,7 @@ class AppSettings {
       appDebugLogEnabled: appDebugLogEnabled ?? this.appDebugLogEnabled,
       batteryChemistryByDeviceId:
           batteryChemistryByDeviceId ?? this.batteryChemistryByDeviceId,
+      unitSystem: unitSystem ?? this.unitSystem,
     );
   }
 }