feat(frontend): avatar upload QOL — feedback, re-crop, drop, progress, history

Task 12 batch around the existing crop/preview flow:
- Success Notice (auto-dismiss ~2.5s) after an avatar upload.
- "Reposition" re-crops the current avatar without re-picking a file.
- Drag & drop an image straight onto the profile avatar circle.
- Real upload progress via a new XHR-backed api.upload (fetch has none);
  refreshOnce now also stores the renewed token (reload-restore fix).
- Local avatar history (last 5, IndexedDB, this-device-only) strip that
  re-uploads a stored crop. Stored as ArrayBuffer (Blob is not cloneable
  under structuredClone); label makes the per-device scope explicit.
- Added a "success" tone to Notice.

Infra (same session): registered @shared/@features/@pages/@app/@test path
aliases in vite.config + tsconfigs and rewrote deep ../../../ imports;
moved avatar components into components/avatar/ to keep folders at <=4 files.

Tests: avatarHistory cap/order, recrop visibility, drop-opens-cropper,
client upload/progress/401-retry. bun test 103 pass, lint 0 errors, build ok.

frontend/src/pages/app/LinkPage.tsx

@@ -1,6 +1,6 @@
 import { useTranslation } from 'react-i18next'
-import { LinkDeviceForm } from '../../features/device-link/LinkDeviceForm'
-import { PageTitle } from '../../shared/layout/PageTitle'
+import { LinkDeviceForm } from '@features/device-link/LinkDeviceForm'
+import { PageTitle } from '@shared/layout/PageTitle'
 
 const STEPS = ['one', 'two', 'three'] as const