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/miniPlayer/components/MiniControls.tsx

@@ -1,5 +1,5 @@
 import { Pause, Play, SkipBack, SkipForward } from 'lucide-react';
-import { formatTrackTime } from '@/utils/format/formatDuration';
+import { formatTrackTime } from '@/lib/format/formatDuration';
 import type { MiniControlAction } from '@/features/miniPlayer/utils/miniPlayerBridge';
 
 interface Props {

src/features/miniPlayer/components/MiniTitlebar.tsx

@@ -1,6 +1,6 @@
 import { Maximize2, Pin, PinOff, X } from 'lucide-react';
 import type { TFunction } from 'i18next';
-import { IS_LINUX } from '@/utils/platform';
+import { IS_LINUX } from '@/lib/util/platform';
 
 interface Props {
   trackTitle: string | undefined;

src/features/miniPlayer/hooks/useMiniWindowSetup.ts

@@ -1,7 +1,7 @@
 import { useEffect } from 'react';
 import { invoke } from '@tauri-apps/api/core';
 import { useAuthStore } from '@/store/authStore';
-import { IS_LINUX } from '@/utils/platform';
+import { IS_LINUX } from '@/lib/util/platform';
 import {
   EXPANDED_SIZE, EXPANDED_MIN, readStoredExpandedHeight,
 } from '@/features/miniPlayer/utils/miniPlayerHelpers';