feat(discovery): Navidrome AudioMuse-AI client integration and library scoping

Add per-server toggle for AudioMuse-style discovery: Instant Mix via
getSimilarSongs, server similar artists instead of Last.fm on artist pages,
and higher similar-artist count in Now Playing when enabled.

When browsing a single music folder, filter similar/top song results by
album ids from that scope (Navidrome does not apply musicFolderId to those
endpoints). Request larger similar batches under a narrow scope.

Keep radio-from-track as two blocks (shuffled top songs, then shuffled
similar-by-artist) so it differs from Instant Mix. Show Alpha badge beside
the setting. Add research/ to .gitignore.

src/locales/nl.ts

@@ -94,6 +94,7 @@ export const nlTranslation = {
     addToQueue: 'Aan wachtrij toevoegen',
     enqueueAlbum: 'Album in wachtrij',
     startRadio: 'Radio starten',
+    instantMix: 'Instant Mix',
     lfmLove: 'Liken op Last.fm',
     lfmUnlove: 'Niet meer liken op Last.fm',
     favorite: 'Favoriet',
@@ -396,6 +397,9 @@ export const nlTranslation = {
     testBtn: 'Verbinding testen',
     testingBtn: 'Testen…',
     serverCompatible: 'Compatibel met: Navidrome · Gonic · Airsonic · Subsonic',
+    audiomuseTitle: 'AudioMuse-AI (Navidrome)',
+    audiomuseDesc:
+      'Zet aan als deze server de AudioMuse-AI Navidrome-plugin gebruikt. Schakelt Instant Mix per nummer in en toont vergelijkbare artiesten van de server i.p.v. Last.fm op artiestpagina’s.',
     connected: 'Verbonden',
     failed: 'Mislukt',
     eqTitle: 'Equalizer',