feat: add create_tray() factory with platform dispatch

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

whisper_local/tray/__init__.py

@@ -1 +1,20 @@
-"""Tray-Package — wird in späteren Tasks befüllt."""
+"""Tray-Package — plattformspezifische Tray-App."""
+
+import sys
+from typing import Callable
+
+from whisper_local.tray._tray import AppState, NoOpTray
+
+
+def create_tray(
+    on_settings: Callable[[], None],
+    on_quit: Callable[[], None],
+) -> "Win32TrayApp | NoOpTray":
+    """Gibt den plattformspezifischen Tray zurück."""
+    if sys.platform == "win32":
+        from whisper_local.tray._tray import Win32TrayApp
+        return Win32TrayApp(on_settings=on_settings, on_quit=on_quit)
+    return NoOpTray()
+
+
+__all__ = ["create_tray", "AppState"]