refactor(lib): consolidate generic infra into src/lib

Move domain-agnostic, feature-free helpers out of the flat utils/ and store/
roots into src/lib/ (plan M4, §3 lib/ layer):
- lib/format/: formatBytes, formatClockTime, formatDuration, formatHumanDuration,
  relativeTime (pure format/date/byte/clock helpers)
- lib/i18n.ts: i18next bootstrap (global app infra)
- lib/util/: sanitizeHtml, platform, dedupeById, safeStorage (pure helpers +
  the zustand storage adapter)

playbackScheduleFormat stays in utils/format (runtime usePlayerStore dep =
audio-core coupling, not generic). formatClockTime keeps a type-only
@/store/authStoreTypes import (erased, no runtime inversion — accepted per the
deviceSync precedent).

Pure move via deep @/lib/* specifiers (no barrel → no mock-collapse surface).
tsc 0, lint 0/0, full suite 319 files / 2353 tests green.

Tooling note: lib_move.py regex extended to also rewrite side-effect imports
(import './i18n') and vi.importActual paths — both were silent gaps.

src/features/deviceSync/utils/deviceSyncLegacyTemplate.ts

@@ -1,4 +1,4 @@
-import { IS_WINDOWS } from '@/utils/platform';
+import { IS_WINDOWS } from '@/lib/util/platform';
 
 // Same sanitize rules the Rust side uses (`sanitize_path_component`): strip
 // Windows-illegal chars and control chars, trim leading/trailing dots + spaces.

src/features/deviceSync/utils/runDeviceSyncMigration.ts

@@ -5,7 +5,7 @@ import type { SubsonicSong } from '@/lib/api/subsonicTypes';
 import { applyLegacyTemplate } from '@/features/deviceSync/utils/deviceSyncLegacyTemplate';
 import { trackToSyncInfo } from '@/features/deviceSync/utils/deviceSyncHelpers';
 import { fetchTracksForSource } from '@/utils/playback/fetchTracksForSource';
-import { IS_WINDOWS } from '@/utils/platform';
+import { IS_WINDOWS } from '@/lib/util/platform';
 
 export type MigrationPhase = 'closed' | 'loading' | 'preview' | 'executing' | 'done' | 'nothing';