Handle playlists as results of adding song by "searching"

Basically when typing a string that causes the bot to search youtube, if the first result is a playlist, it doesn't work at the moment. The string "incubus light grenades" is an example that can be used to test with

No files or tests are named in the issue, so start by locating the add-by-search command path that calls YouTube and picks the first hit. Reproduce with the query "incubus light grenades" in the bot to confirm a playlist is returned first and see where the handler assumes a song result. Done is a defined first-result playlist path (playable or explicitly rejected) and a successful search-add flow for that query without runtime errors.

Vom Indexierungsmodell aus dem Issue-Text verfasst.