Add admin access and landing dashboard

TrafagSalesExporter/Services/AccessSessionTracker.cs

@@ -0,0 +1,54 @@
+using System.Collections.Concurrent;
+
+namespace TrafagSalesExporter.Services;
+
+public interface IAccessSessionTracker
+{
+    IReadOnlyList<AccessSessionSnapshot> GetActiveSessions();
+    void Register(string sessionId, string area, string username, string? remoteAddress);
+    void Touch(string sessionId);
+    void Unregister(string sessionId);
+}
+
+public sealed class AccessSessionTracker : IAccessSessionTracker
+{
+    private readonly ConcurrentDictionary<string, AccessSessionSnapshot> _sessions = new(StringComparer.OrdinalIgnoreCase);
+
+    public IReadOnlyList<AccessSessionSnapshot> GetActiveSessions()
+        => _sessions.Values
+            .OrderByDescending(session => session.LastSeenAt)
+            .ToList();
+
+    public void Register(string sessionId, string area, string username, string? remoteAddress)
+    {
+        var now = DateTimeOffset.Now;
+        _sessions[sessionId] = new AccessSessionSnapshot(
+            sessionId,
+            area,
+            username,
+            string.IsNullOrWhiteSpace(remoteAddress) ? "unbekannt" : remoteAddress,
+            now,
+            now);
+    }
+
+    public void Touch(string sessionId)
+    {
+        if (!_sessions.TryGetValue(sessionId, out var session))
+            return;
+
+        _sessions[sessionId] = session with { LastSeenAt = DateTimeOffset.Now };
+    }
+
+    public void Unregister(string sessionId)
+    {
+        _sessions.TryRemove(sessionId, out _);
+    }
+}
+
+public sealed record AccessSessionSnapshot(
+    string SessionId,
+    string Area,
+    string Username,
+    string RemoteAddress,
+    DateTimeOffset StartedAt,
+    DateTimeOffset LastSeenAt);