Docs: migrating off the deprecated spotipy recommendations()/related_artists()

[AliAkhtari78]

Spotify deprecated recommendations and related-artists in the official API (Nov 2024), so many spotipy snippets now 403. Add a short docs page showing the SpotifyScraper equivalent (get_related_artists / the discovery API) with a before/after snippet.

Acceptance criteria

• A before (spotipy, 403) / after (SpotifyScraper, no key) comparison.
• Honest note that audio-features cannot be restored (Spotify removed it).

Pairs with the README wedge; pure docs.