feat(artist-detail): user-configurable visibility and order of page sections (closes #252) (#254)

Per bcorporaal's request in #252: album-oriented listeners want a
cleaner artist page focused on the album grid, with the freedom to
reorder/hide bio, top tracks, and similar artists.

Five sections are now reorder- and toggle-able from Settings →
Personalisation → "Artist page sections": Bio, Top tracks, Similar
artists, Albums, Also featured on. The fixed header block (artist
photo, name, action buttons) stays at the top.

Implementation reuses the existing sidebar customizer pattern:

- new `src/store/artistLayoutStore.ts` modelled on `sidebarStore.ts`
  with the same persist + onRehydrateStorage migration so future-added
  sections don't silently disappear from existing users' configs.
- `ArtistDetail.tsx` render block refactored from a flat sequence of
  conditional JSX into a `renderableSectionIds.map()` driven by the
  store. The "first rendered section gets marginTop: 0" rule now
  works regardless of the configured order — both hidden-by-toggle
  and empty-data sections are filtered before the layout decides
  what's first.
- `ArtistLayoutCustomizer` component in Settings, lifted from
  `LyricsSourcesCustomizer` (drag via `useDragSource` + `psy-drop`
  event, per-row toggle, reset button).
- 7 new i18n keys per locale across all 8 languages.

The store hook MUST stay above the loading / !artist early returns —
otherwise React's hook call order mismatches between renders and the
component fails silently. Lesson learned during the refactor.

Co-authored-by: Psychotoxical <dev@psysonic.app>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/locales/nl.ts

@@ -645,6 +645,14 @@ export const nlTranslation = {
     homeCustomizerTitle: 'Startpagina',
     sidebarTitle: 'Zijbalk',
     sidebarReset: 'Standaard herstellen',
+    artistLayoutTitle: 'Secties artiestenpagina',
+    artistLayoutDesc: 'Versleep om te herschikken, schakel om individuele secties van de artiestenpagina te verbergen. Secties zonder gegevens worden automatisch overgeslagen.',
+    artistLayoutReset: 'Standaard herstellen',
+    artistLayoutBio: 'Biografie van de artiest',
+    artistLayoutTopTracks: 'Populaire nummers',
+    artistLayoutSimilar: 'Soortgelijke artiesten',
+    artistLayoutAlbums: 'Albums',
+    artistLayoutFeatured: 'Ook te horen op',
     sidebarDrag: 'Slepen om te herordenen',
     sidebarFixed: 'Altijd zichtbaar',
     randomNavSplitTitle: 'Mix-navigatie splitsen',