8 test files had _DummyConfigManager missing get_active_media_server(),
causing failures when pytest ran them before the test file that had it.
Whichever file set sys.modules first won, and the incomplete dummy broke
later tests. Also fix script.js read_text() missing encoding='utf-8'
which failed on non-UTF-8 default locales.
Use the shared metadata source priority when resolving album IDs,
album searches, and tracklists in track number repair.
Keeps Deezer and iTunes ahead of Spotify where configured, while
still allowing the job to fall back through other supported sources.
