v0.37.0: Import from URL takes Spotify links

A Spotify track, album or playlist is read off Spotify's public embed
page, each song found on YouTube by the result closest to Spotify's
length, downloaded with the song flags, tagged with Spotify's
artist/title/album/track number, then imported and identified.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_round75.py

@@ -362,6 +362,8 @@ def test_only_the_chosen_songs_download(window, qapp, fake, mp3_file,
             return False
         def chosen_entries(self):
             return chosen
+        def spotify_tracks(self):
+            return []
         def download_urls(self):
             return [c["url"] for c in chosen]
     monkeypatch.setattr(mw, "UrlImportDialog", _Dialog)
@@ -406,6 +408,8 @@ def test_one_song_gets_no_progress_window(window, qapp, fake, mp3_file,
             return False
         def chosen_entries(self):
             return []
+        def spotify_tracks(self):
+            return []
         def download_urls(self):
             return [self.url()]
     monkeypatch.setattr(mw, "UrlImportDialog", _Dialog)