SwyxTray und Firefox-Plugin in das Repository aufnehmen

Windows-Tray-Anwendung (CLMgr-Anbindung an SwyxIt!) samt WebSocket-Zugang,
Firefox-Erweiterung und Browser-Beispielclient.

src/SwyxTray/Log.cs

@@ -0,0 +1,67 @@
+using System.Text;
+
+namespace SwyxTray;
+
+/// <summary>
+/// Schlankes Dateiprotokoll unter %LOCALAPPDATA%\SwyxTray\. Bewusst ohne
+/// Framework: die App hat kein Fenster, ein Protokoll ist deshalb das einzige
+/// Mittel zur Fehlersuche.
+/// </summary>
+internal static class Log
+{
+    private const long MaxBytes = 1024 * 1024;
+    private static readonly object Gate = new();
+
+    public static bool VerboseEnabled { get; set; }
+
+    public static string Directory { get; } = Path.Combine(
+        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
+        "SwyxTray");
+
+    public static string FilePath { get; } = Path.Combine(Directory, "swyxtray.log");
+
+    public static void Debug(string message)
+    {
+        if (VerboseEnabled)
+        {
+            Write("DBG", message);
+        }
+    }
+
+    public static void Info(string message) => Write("INF", message);
+
+    public static void Error(string message, Exception? ex = null)
+        => Write("ERR", ex is null ? message : $"{message} :: {ex}");
+
+    private static void Write(string level, string message)
+    {
+        var line = $"{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff} [{level}] {message}{Environment.NewLine}";
+
+        lock (Gate)
+        {
+            try
+            {
+                System.IO.Directory.CreateDirectory(Directory);
+                RollIfTooLarge();
+                File.AppendAllText(FilePath, line, Encoding.UTF8);
+            }
+            catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+            {
+                // Ein fehlschlagendes Protokoll darf die App nicht beenden.
+            }
+        }
+    }
+
+    private static void RollIfTooLarge()
+    {
+        var info = new FileInfo(FilePath);
+        if (!info.Exists || info.Length < MaxBytes)
+        {
+            return;
+        }
+
+        var backup = FilePath + ".1";
+        File.Delete(backup);
+        File.Move(FilePath, backup);
+    }
+}