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/Services/PointLogger.cs

@@ -0,0 +1,67 @@
+using FieldLogger.Models;
+using FieldLogger.Services.Data;
+using Microsoft.Extensions.Logging;
+
+namespace FieldLogger.Services;
+
+/// <summary>
+/// Joins UM receiver log packets with the current GNSS fix and persists them
+/// under the active job. Runs for the lifetime of the app.
+/// </summary>
+public sealed class PointLogger
+{
+    private readonly UmReceiverService _locator;
+    private readonly MaglinkService _gps;
+    private readonly AppDatabase _database;
+    private readonly SettingsService _settings;
+    private readonly ILogger<PointLogger> _logger;
+
+    /// <summary>Raised (on the UI thread) after a point is saved.</summary>
+    public event EventHandler<LoggedPoint>? PointSaved;
+
+    /// <summary>Raised when a packet arrives but no active job is selected, so the point was dropped.</summary>
+    public event EventHandler? PacketIgnoredNoJob;
+
+    public PointLogger(UmReceiverService locator, MaglinkService gps, AppDatabase database,
+        SettingsService settings, ILogger<PointLogger> logger)
+    {
+        _locator = locator;
+        _gps = gps;
+        _database = database;
+        _settings = settings;
+        _logger = logger;
+
+        _locator.PacketReceived += OnPacketReceived;
+    }
+
+    private void OnPacketReceived(object? sender, UmLogPacket packet)
+    {
+        _ = HandlePacketAsync(packet);
+    }
+
+    private async Task HandlePacketAsync(UmLogPacket packet)
+    {
+        try
+        {
+            var jobId = _settings.ActiveJobId;
+            if (jobId is null)
+            {
+                _logger.LogWarning("Log packet received but no active job; point dropped");
+                MainThread.BeginInvokeOnMainThread(() => PacketIgnoredNoJob?.Invoke(this, EventArgs.Empty));
+                return;
+            }
+
+            var fix = _gps.FreshFix();
+            var point = LoggedPoint.From(jobId.Value, packet, _locator.DeviceInfo, fix, _gps.DeviceInfo);
+            await _database.AddPointAsync(point);
+
+            _logger.LogInformation("Point {Id} saved to job {JobId} (gps valid: {GpsValid})",
+                point.Id, jobId, point.GpsValid);
+            MainThread.BeginInvokeOnMainThread(() => PointSaved?.Invoke(this, point));
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to save logged point");
+        }
+    }
+}