feat: Refactor playlist management, error handling, and testing infrastructure

- Improved playlist item handling with pagination, error logging, and dedicated request hooks.
- Consolidated reusable helpers for track ID normalization, playlist validation, and removal logic.
- Enhanced error handling by introducing `PlaylistNotFound` and `UserNotAuthenticated` exceptions.
- Refined Pytest `qapp` fixture for headless CI compatibility and session-scoped reuse.
- Replaced redundant fixtures in multiple test files for consistency.
- Improved playlist management GUI with detailed debug logging for notifications and operations.
- Added `deptry` configuration to handle transitive dependencies and ignored exclusions.
- Updated Pytest and Tox configurations for consistent environment setup during CI/CD runs.

tests/conftest.py

@@ -1,3 +1,6 @@
+import os
+import tempfile
+from pathlib import Path
 from unittest.mock import Mock
 
 import pytest
@@ -6,14 +9,24 @@ from tidalapi import Album, Track, Video
 from tidalapi.artist import Artist
 
 
-@pytest.fixture
-def qt_app():
-    """Create a QApplication instance for testing Qt widgets."""
-    app = QtWidgets.QApplication.instance()
-    if app is None:
-        app = QtWidgets.QApplication([])
+@pytest.fixture(scope="session")
+def qapp():
+    """Provide a QApplication configured for headless CI (offscreen/minimal)."""
+    # Ensure headless backend for CI runners
+    os.environ.setdefault("QT_QPA_PLATFORM", "offscreen")
+    # Qt expects XDG_RUNTIME_DIR to exist with correct permissions
+    runtime_dir = Path(tempfile.mkdtemp(prefix="xdg-runtime-")).resolve()
+    os.environ.setdefault("XDG_RUNTIME_DIR", str(runtime_dir))
+
+    # Lower graphical requirements
+    QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_DisableHighDpiScaling, True)
+
+    app = QtWidgets.QApplication.instance() or QtWidgets.QApplication([])
     yield app
-    # Note: don't quit the app as it may be shared across tests
+
+
+# Backward compatible alias
+qt_app = qapp
 
 
 @pytest.fixture

tests/test_delimiters_category.py

@@ -9,15 +9,6 @@ from tidal_dl_ng.dialog import DialogPreferences
 from tidal_dl_ng.ui.dialog_settings import Ui_DialogSettings
 
 
-@pytest.fixture
-def qapp():
-    """Create QApplication instance for tests."""
-    app = QtWidgets.QApplication.instance()
-    if app is None:
-        app = QtWidgets.QApplication([])
-    yield app
-
-
 class TestDelimitersPage:
     """Test the Delimiters page specifically."""
 

tests/test_dialog_preferences_integration.py

@@ -9,15 +9,6 @@ from tidal_dl_ng.config import Settings
 from tidal_dl_ng.dialog import DialogPreferences
 
 
-@pytest.fixture
-def qapp():
-    """Create QApplication instance for tests."""
-    app = QtWidgets.QApplication.instance()
-    if app is None:
-        app = QtWidgets.QApplication([])
-    yield app
-
-
 @pytest.fixture
 def mock_settings():
     """Create a mock Settings object with all required attributes."""

tests/test_settings_dialog_structure.py

@@ -1,20 +1,10 @@
 """Tests for the settings dialog category structure and organization."""
 
-import pytest
 from PySide6 import QtCore, QtWidgets
 
 from tidal_dl_ng.ui.dialog_settings import Ui_DialogSettings
 
 
-@pytest.fixture
-def qapp():
-    """Create QApplication instance for tests."""
-    app = QtWidgets.QApplication.instance()
-    if app is None:
-        app = QtWidgets.QApplication([])
-    yield app
-
-
 class TestSettingsDialogStructure:
     """Test the structural integrity of the settings dialog."""
 

tests/test_settings_ui.py

@@ -10,16 +10,6 @@ from tidal_dl_ng.dialog import DialogPreferences
 from tidal_dl_ng.ui.dialog_settings import Ui_DialogSettings
 
 
-@pytest.fixture
-def qapp():
-    """Create QApplication instance for tests."""
-    app = QtWidgets.QApplication.instance()
-    if app is None:
-        app = QtWidgets.QApplication([])
-    yield app
-    # Cleanup is handled by pytest-qt if available, otherwise by QApplication
-
-
 class TestUiDialogSettings:
     """Test the generated UI class."""