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/nowPlaying.ts

@@ -0,0 +1,47 @@
+export const nowPlaying = {
+  tooltip: 'Who is listening?',
+  title: 'Who is listening?',
+  loading: 'Loading…',
+  nobody: 'Nobody is currently listening.',
+  minutesAgo: '{{n}}m ago',
+  nothingPlaying: 'Nothing playing yet. Start a track!',
+  aboutArtist: 'About the Artist',
+  fromAlbum: 'From this Album',
+  viewAlbum: 'View Album',
+  goToArtist: 'Go to Artist',
+  readMore: 'Read more',
+  showLess: 'Show less',
+  genreInfo: 'Genre',
+  trackInfo: 'Track Info',
+  topSongs: 'Most played by this artist',
+  topSongsCredit: 'Top tracks from {{name}}',
+  trackPosition: 'Track {{pos}}',
+  playsCount_one: '{{count}} play',
+  playsCount_other: '{{count}} plays',
+  releasedYearsAgo_one: '{{count}} year ago',
+  releasedYearsAgo_other: '{{count}} years ago',
+  discography: 'Discography',
+  lastfmStats: 'Last.fm stats',
+  thisTrack: 'This track',
+  thisArtist: 'This artist',
+  listeners: 'listeners',
+  scrobbles: 'scrobbles',
+  yourScrobbles: 'by you',
+  listenersN: '{{n}} listeners',
+  scrobblesN: '{{n}} scrobbles',
+  playsByYouN: 'played {{n}}× by you',
+  openTrackOnLastfm: 'Track on Last.fm',
+  openArtistOnLastfm: 'Artist on Last.fm',
+  rgTrackTooltip: 'ReplayGain (track)',
+  rgAlbumTooltip: 'ReplayGain (album)',
+  rgAutoTooltip: 'ReplayGain (auto)',
+  showMoreTracks: 'Show {{count}} more',
+  showLessTracks: 'Show less',
+  hideCard: 'Hide card',
+  layoutMenu: 'Layout',
+  visibleCards: 'Visible cards',
+  hiddenCards: 'Hidden cards',
+  noHiddenCards: 'No hidden cards',
+  resetLayout: 'Reset layout',
+  emptyColumn: 'Drop cards here',
+};