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/nl/queue.ts

@@ -0,0 +1,45 @@
+export const queue = {
+  title: 'Wachtrij',
+  savePlaylist: 'Afspeellijst opslaan',
+  updatePlaylist: 'Afspeellijst bijwerken',
+  filterPlaylists: 'Afspeellijsten filteren…',
+  playlistName: 'Naam afspeellijst',
+  cancel: 'Annuleren',
+  save: 'Opslaan',
+  loadPlaylist: 'Afspeellijst laden',
+  loading: 'Laden…',
+  noPlaylists: 'Geen afspeellijsten gevonden.',
+  load: 'Wachtrij vervangen & afspelen',
+  appendToQueue: 'Toevoegen aan wachtrij',
+  delete: 'Verwijderen',
+  deleteConfirm: 'Afspeellijst "{{name}}" verwijderen?',
+  clear: 'Leegmaken',
+  shuffle: 'Wachtrij shufflen',
+  gapless: 'Naadloos',
+  crossfade: 'Overgang',
+  infiniteQueue: 'Oneindige wachtrij',
+  autoAdded: '— Automatisch toegevoegd —',
+  radioAdded: '— Radio —',
+  hide: 'Verbergen',
+  hideNowPlaying: 'Now playing info verbergen',
+  showNowPlaying: 'Now playing info weergeven',
+  close: 'Sluiten',
+  nextTracks: 'Volgende nummers',
+  shareQueue: 'Wachtrij-deellink kopiëren',
+  shareQueueEmpty: 'De wachtrij is leeg — niets om te delen.',
+  emptyQueue: 'De wachtrij is leeg.',
+  trackSingular: 'nummer',
+  trackPlural: 'nummers',
+  showRemaining: 'Resterende tijd tonen',
+  showTotal: 'Totale tijd tonen',
+  showEta: 'Geschatte eindtijd tonen',
+  replayGain: 'ReplayGain',
+  rgTrack: 'T {{db}} dB',
+  rgAlbum: 'A {{db}} dB',
+  rgPeak: 'Piek {{pk}}',
+  sourceOffline: 'Afspelen vanuit offlinebibliotheek',
+  sourceHot: 'Afspelen vanuit cache',
+  sourceStream: 'Afspelen vanuit netwerkstream',
+  clearCachedLoudnessWaveform: 'Clear cached loudness and waveform, then re-analyze this track',
+  recalculatingLoudnessWaveform: 'Recalculating loudness and waveform for this track…',
+};