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/fullscreenPlayer/components/FsClock.tsx

@@ -1,7 +1,7 @@
 import { memo, useEffect, useState } from 'react';
 import { useTranslation } from 'react-i18next';
 import { useAuthStore } from '@/store/authStore';
-import { formatClockTime } from '@/utils/format/formatClockTime';
+import { formatClockTime } from '@/lib/format/formatClockTime';
 
 /**
  * Standalone wall-clock for the fullscreen player. Owns its own state so the

src/features/fullscreenPlayer/components/FsQueueModal.tsx

@@ -8,7 +8,7 @@ import {
   getQueueResolverVersion,
   subscribeQueueResolver,
 } from '@/utils/library/queueTrackResolver';
-import { formatTrackTime } from '@/utils/format/formatDuration';
+import { formatTrackTime } from '@/lib/format/formatDuration';
 
 interface Props {
   onClose: () => void;

src/features/fullscreenPlayer/components/FsTimeReadout.tsx

@@ -1,6 +1,6 @@
 import { memo, useEffect, useRef } from 'react';
 import { getPlaybackProgressSnapshot, subscribePlaybackProgress } from '@/store/playbackProgress';
-import { formatTrackTime } from '@/utils/format/formatDuration';
+import { formatTrackTime } from '@/lib/format/formatDuration';
 
 /**
  * Centered "current / total" readout for the control bar. Updates the current