Initial commit: FieldLogger MAUI app with Maglink BLE support

Added Maglink RTK GNSS receiver integration with correct BLE UUIDs and device name filtering (ML-* prefix).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

FieldLogger/Converters/AppConverters.cs

@@ -0,0 +1,68 @@
+using System.Globalization;
+using FieldLogger.Models;
+using FieldLogger.Services;
+
+namespace FieldLogger.Converters;
+
+public sealed class ConnectionStateToColorConverter : IValueConverter
+{
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        value switch
+        {
+            ConnectionState.Connected => Colors.LimeGreen,
+            ConnectionState.Connecting => Colors.Orange,
+            _ => Colors.IndianRed,
+        };
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}
+
+public sealed class ConnectionStateToTextConverter : IValueConverter
+{
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        value switch
+        {
+            ConnectionState.Connected => "Connected",
+            ConnectionState.Connecting => "Connecting…",
+            _ => "Disconnected",
+        };
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}
+
+public sealed class UtilityToNameConverter : IValueConverter
+{
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        value is int i ? ((UmUtility)i).ToString() : "";
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}
+
+public sealed class InvertBoolConverter : IValueConverter
+{
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => value is bool b && !b;
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => value is bool b && !b;
+}
+
+public sealed class FixStatusToNameConverter : IValueConverter
+{
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        value is int i ? (GnssFixStatus)i switch
+        {
+            GnssFixStatus.NoFix => "No Fix",
+            GnssFixStatus.Single => "Single",
+            GnssFixStatus.Dgps => "DGPS",
+            GnssFixStatus.RtkFixed => "RTK Fixed",
+            GnssFixStatus.RtkFloat => "RTK Float",
+            _ => "?",
+        } : "—";
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}