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/ViewModels/MapViewModel.cs

@@ -0,0 +1,53 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using FieldLogger.Models;
+using FieldLogger.Services;
+using FieldLogger.Services.Data;
+
+namespace FieldLogger.ViewModels;
+
+[QueryProperty(nameof(JobId), "jobId")]
+public sealed partial class MapViewModel : ObservableObject
+{
+    private readonly AppDatabase _database;
+    private readonly SettingsService _settings;
+
+    /// <summary>Job to display; 0 means "use the active job".</summary>
+    [ObservableProperty]
+    private int _jobId;
+
+    [ObservableProperty]
+    private string _jobName = "";
+
+    [ObservableProperty]
+    private string _statusText = "";
+
+    public SettingsService Settings => _settings;
+
+    public MapViewModel(AppDatabase database, SettingsService settings)
+    {
+        _database = database;
+        _settings = settings;
+    }
+
+    /// <summary>Loads the points to plot (only points with a valid GNSS position).</summary>
+    public async Task<List<LoggedPoint>> LoadPointsAsync()
+    {
+        var jobId = JobId > 0 ? JobId : _settings.ActiveJobId;
+        if (jobId is null)
+        {
+            JobName = "";
+            StatusText = "No job selected. Create or activate a job to see its points.";
+            return new List<LoggedPoint>();
+        }
+
+        var job = await _database.GetJobAsync(jobId.Value);
+        JobName = job?.Name ?? "";
+
+        var all = await _database.GetPointsAsync(jobId.Value);
+        var plottable = all.Where(p => p.GpsValid).ToList();
+        StatusText = plottable.Count == all.Count
+            ? $"{JobName}: {all.Count} points"
+            : $"{JobName}: {plottable.Count} of {all.Count} points have GPS positions";
+        return plottable;
+    }
+}