Saves successfully loaded playlist URLs to localStorage and displays
them as clickable pills between the input bar and playlist container.
Clicking a pill re-loads that URL; X button removes it. Max 10 per
source, most recent first. Source-colored hover accents match each
tab's brand styling.
Also fixes duplicate playlist bug — YouTube and Spotify Public now
check for already-loaded playlists before making API calls, preventing
broken duplicate cards when the same URL is entered twice.
a02d14a23a
