fix(label): rewrite track row, add jump-nav, fix description border

- Replace track row with ArtistDetailView pattern (favorites, TrackMenu, radio)
- Add sticky jump-nav bar with IntersectionObserver for all sections
- Fix description border leak with CSS reset
- Make "More labels" containers round
- Wire onTrackAddFavorite prop in +page.svelte
- Add i18n keys: label.about, label.otherLabels (all 4 locales)

src/lib/i18n/locales/fr.json

@@ -83,6 +83,8 @@
   },
   "label": {
     "title": "Label",
+    "about": "À propos",
+    "otherLabels": "Autres labels",
     "popularTracks": "Titres populaires",
     "releases": "Sorties",
     "criticsPicks": "Choix des critiques",