refactor: Restructure GUI components into separate modules for improved maintainability

tidal_dl_ng/gui/__init__.py

@@ -0,0 +1,19 @@
+"""GUI module for TIDAL Downloader Next Generation.
+
+This module provides the main window and all GUI-related functionality
+organized into manageable components.
+"""
+
+try:
+    from PySide6 import QtCore, QtGui, QtWidgets
+except ImportError:  # pragma: no cover - GUI deps optional in some environments
+    QtCore = QtGui = QtWidgets = None
+
+from tidal_dl_ng.gui.main_window import MainWindow
+
+__all__ = [
+    "MainWindow",
+    "QtCore",
+    "QtGui",
+    "QtWidgets",
+]