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/search.ts

@@ -0,0 +1,29 @@
+export const search = {
+  placeholder: 'Search for artist, album or song…',
+  noResults: 'No results for "{{query}}"',
+  artists: 'Artists',
+  albums: 'Albums',
+  songs: 'Songs',
+  clearLabel: 'Clear search',
+  addedToQueueToast: 'Added "{{title}}" to queue',
+  title: 'Search',
+  resultsFor: 'Results for "{{query}}"',
+  album: 'Album',
+  advanced: 'Advanced Search',
+  advancedSearchTerm: 'Search term',
+  advancedSearchPlaceholder: 'Title, album, artist…',
+  advancedGenre: 'Genre',
+  advancedAllGenres: 'All genres',
+  advancedYear: 'Year',
+  advancedYearFrom: 'from',
+  advancedYearTo: 'to',
+  advancedAll: 'All',
+  advancedSearch: 'Search',
+  advancedEmpty: 'Enter a search term or select a filter to begin.',
+  advancedNoResults: 'No results found.',
+  advancedGenreNote: 'Songs are randomly selected from this genre.',
+  recentSearches: 'Recent Searches',
+  browse: 'Browse',
+  emptyHint: 'What do you want to hear?',
+  genres: 'Genres',
+};