refactor(i18n): split locale files into per-namespace modules (Phase K) (#688)

Each src/locales/<lang>.ts (~1800 LOC) becomes a folder src/locales/<lang>/
with one module per i18n namespace (44 each) plus an index.ts barrel that
reassembles <lang>Translation in the original key order.

Mechanical, script-driven split with a JSON round-trip check: every
locale object is byte-identical to its pre-split form. i18n.ts is
unchanged — './locales/<lang>' now resolves to the folder index.

The per-namespace settings.ts files land ~440-460 LOC; a single i18n
namespace is the natural, non-arbitrary split unit for a flat string
table, so they are intentionally left whole.

src/locales/en/home.ts

@@ -0,0 +1,19 @@
+export const home = {
+  hero: 'Featured',
+  starred: 'Personal Favorites',
+  recent: 'Recently Added',
+  mostPlayed: 'Most Played',
+  recentlyPlayed: 'Recently Played',
+  losslessAlbums: 'Lossless Albums',
+  discover: 'Discover',
+  discoverSongs: 'Discover Songs',
+  loadMore: 'Load More',
+  discoverMore: 'Discover More',
+  discoverArtists: 'Discover Artists',
+  discoverArtistsMore: 'All Artists',
+  becauseYouLike: 'Because you listened…',
+  becauseYouLikeFor: 'Because you listened to {{artist}}',
+  similarTo: 'Similar to {{artist}}',
+  becauseYouLikeTracks_one: '{{count}} track',
+  becauseYouLikeTracks_other: '{{count}} tracks'
+};