fix: Use correct SI units for speed test conversion

- Change "Kb" to "kb" for kilo prefix (SI standard uses lowercase k)
- Replace binary conversion (* 1024) with SI conversion (* 1000) for Kbps to bps
- Update related test expectations

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: AustinChangLinksys

lib/page/health_check/providers/health_check_provider.dart

@@ -155,7 +155,7 @@ class HealthCheckProvider extends Notifier<HealthCheckState> {
       });
     } else {
       // Add a random value to simulate a fluctuating meter during tests.
-      final randomValue = (_random.nextDouble() * (15 - (-3)) + (-3)) * 1024;
+      final randomValue = (_random.nextDouble() * (15 - (-3)) + (-3)) * 1000;
       meterValue += randomValue;
     }
 

lib/page/health_check/services/health_check_service.dart

@@ -186,11 +186,11 @@ class SpeedTestService {
       return SpeedTestUIModel.empty();
     }
     final download = NetworkUtils.formatBitsWithUnit(
-      (speedTestResult.downloadBandwidth ?? 0) * 1024,
+      (speedTestResult.downloadBandwidth ?? 0) * 1000,
       decimals: 1,
     );
     final upload = NetworkUtils.formatBitsWithUnit(
-      (speedTestResult.uploadBandwidth ?? 0) * 1024,
+      (speedTestResult.uploadBandwidth ?? 0) * 1000,
       decimals: 1,
     );
     final (formattedTimestamp, _) = _formatTimestamp(timestamp ?? '');

lib/page/health_check/shared_widgets/speed_test_widget.dart

@@ -225,13 +225,13 @@ class SpeedTestWidget extends ConsumerWidget {
     final result = state.result ?? SpeedTestUIModel.empty();
     // Format the live meter value for display.
     final formattedLiveValue = NetworkUtils.formatBitsWithUnit(
-        (state.meterValue * 1024).toInt(),
+        (state.meterValue * 1000).toInt(),
         decimals: 1);
 
     final bandwidthValue = formattedLiveValue.value;
     final bandwidthUnit = formattedLiveValue.unit;
 
-    final meterValueMbps = (state.meterValue / 1024);
+    final meterValueMbps = (state.meterValue / 1000);
 
     return Center(
       child: AppGauge(

lib/utils.dart

@@ -330,7 +330,7 @@ extension MediaQueryUtils on Utils {
 extension NetworkUtils on Utils {
   /// Formats a bit count into a human-readable string with SI units (base 1000).
   ///
-  /// Example: 1000 bits -> "1 Kb"
+  /// Example: 1000 bits -> "1 kb"
   static String formatBits(int bits, {int decimals = 0}) {
     final result = formatBitsWithUnit(bits, decimals: decimals);
     return '${result.value} ${result.unit}';
@@ -342,7 +342,7 @@ extension NetworkUtils on Utils {
   static ({String value, String unit}) formatBitsWithUnit(int bits,
       {int decimals = 0}) {
     if (bits <= 0) return (value: '0', unit: "b");
-    const suffixes = ["b", "Kb", "Mb", "Gb", "Tb", "Pb"];
+    const suffixes = ["b", "kb", "Mb", "Gb", "Tb", "Pb"];
     var i = (log(bits) / log(1000)).floor();
     var number = (bits / pow(1000, i));
     return (

test/utils_test.dart

@@ -510,7 +510,7 @@ void main() {
     test('formatBits: formats bits in kilobytes range with specified decimals',
         () {
       const bits = 1234;
-      const expected = '1.234 Kb';
+      const expected = '1.234 kb';
 
       final formattedBits = NetworkUtils.formatBits(bits, decimals: 3);
       expect(formattedBits, expected);
@@ -565,18 +565,18 @@ void main() {
       expect(result.unit, 'b');
     });
 
-    test('formats bits (less than 1Kb)', () {
+    test('formats bits (less than 1kb)', () {
       const bits = 500;
       final result = NetworkUtils.formatBitsWithUnit(bits);
       expect(result.value, '500');
       expect(result.unit, 'b');
     });
 
     test('formats kilobytes with 0 decimal places', () {
-      const bits = 2000; // 2 Kb
+      const bits = 2000; // 2 kb
       final result = NetworkUtils.formatBitsWithUnit(bits);
       expect(result.value, '2');
-      expect(result.unit, 'Kb');
+      expect(result.unit, 'kb');
     });
 
     test('formats megabytes with 2 decimal places', () {