feat(hover): add track details preview on hover + fix all ruff violations

Implement comprehensive track information display on hover and resolve all
code quality issues to achieve complete ruff compliance.

MAJOR FEATURES:
- Track details preview on hover with rich metadata display
- Async BPM fetching with loading indicator
- Enhanced metadata utilities with fuzzy matching
- TIDAL API extras integration

FILES MODIFIED: 15+ files (core, UI, tests, docs)

RUFF COMPLIANCE: 0 errors (89+ violations resolved)
- Fixed E999 syntax error in metadata_utils.py
- Refactored 10+ complex functions (C901)
- Updated error handling (S110, S112, SIM105)
- Modernized type hints (UP038)
- Fixed naming conflicts (A001, F811)

BUG FIXES:
- Added missing _on_update_cover() method (11 test failures)
- Fixed BPM display and async loading
- Improved thread safety

TESTING: 30 passed, 1 skipped
DOCUMENTATION: Windows PowerShell support, tox troubleshooting

tests/conftest.py

@@ -0,0 +1,115 @@
+from unittest.mock import Mock
+
+import pytest
+from PySide6 import QtCore, QtGui, QtWidgets
+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([])
+    yield app
+    # Note: don't quit the app as it may be shared across tests
+
+
+@pytest.fixture
+def info_tab_widget(qt_app):
+    """Create an InfoTabWidget instance for testing."""
+    from tidal_dl_ng.ui.info_tab_widget import InfoTabWidget
+
+    widget = InfoTabWidget()
+    yield widget
+    # InfoTabWidget inherits from QObject, not QWidget, so it doesn't have close()
+    widget.deleteLater()
+
+
+@pytest.fixture
+def mock_track():
+    """Create a mock Track object with metadata."""
+    track = Mock(spec=Track)
+    track.name = "Bohemian Rhapsody"
+    track.title = "Bohemian Rhapsody"
+    track.full_name = "Bohemian Rhapsody"
+    track.version = "2011 Remaster"
+    track.duration = 354  # 5:54
+    track.explicit = False
+    track.popularity = 95
+    track.bpm = 72
+    track.isrc = "GBUM71029604"
+    track.bit_depth = 24
+    track.sample_rate = 96000
+    track.audio_modes = []
+    track.media_metadata_tags = []
+    track.available = True
+    track.id = 12345
+
+    # Mock album
+    mock_album = Mock(spec=Album)
+    mock_album.name = "A Night at the Opera"
+    mock_album.id = 67890
+    mock_album.release_date = Mock()
+    mock_album.release_date.strftime = Mock(return_value="1975-11-21")
+    track.album = mock_album
+
+    # Mock artists
+    mock_artist = Mock(spec=Artist)
+    mock_artist.name = "Queen"
+    mock_artist.roles = [Mock(name="main")]
+    track.artists = [mock_artist]
+
+    return track
+
+
+@pytest.fixture
+def mock_video():
+    """Create a mock Video object."""
+    video = Mock(spec=Video)
+    video.name = "Thriller"
+    video.title = "Thriller"
+    video.full_name = "Thriller (Official Video)"
+    video.duration = 600
+    video.explicit = False
+    video.video_quality = "1080p"
+    video.available = True
+    video.id = 54321
+
+    mock_artist = Mock(spec=Artist)
+    mock_artist.name = "Michael Jackson"
+    video.artists = [mock_artist]
+
+    mock_album = Mock(spec=Album)
+    mock_album.name = "Thriller"
+    video.album = mock_album
+
+    return video
+
+
+@pytest.fixture
+def tree_view_setup(qt_app):
+    """Create a tree view with model for testing hover manager."""
+    tree_view = QtWidgets.QTreeView()
+    source_model = QtGui.QStandardItemModel()
+    proxy_model = QtCore.QSortFilterProxyModel()
+
+    proxy_model.setSourceModel(source_model)
+    tree_view.setModel(proxy_model)
+
+    # Add some test data
+    source_model.setColumnCount(2)
+    for i in range(5):
+        item_index = QtGui.QStandardItem(f"Item {i}")
+        item_obj = QtGui.QStandardItem()
+        mock_track = Mock(spec=Track)
+        mock_track.name = f"Track {i}"
+        mock_track.id = i
+        item_obj.setData(mock_track, QtCore.Qt.ItemDataRole.UserRole)
+        source_model.appendRow([item_index, item_obj])
+
+    yield tree_view, proxy_model, source_model
+
+    tree_view.close()
+    tree_view.deleteLater()